FIELD OF THE INVENTION
[0001] The present invention relates to estimating precise position of a stationary or moving
object using multiple satellite signals and a network of multiple receivers. The present
invention is particularly suited to position estimation in real-time kinetic environments
where it is desirable to take into account the spatial distribution of the ionosphere
delay.
BACKGROUND OF THE INVENTION
[0002] Satellite navigation systems, such as GPS (USA) and GLONASS (Russia), are intended
for accuracy self-positioning of different users possessing special navigation receivers.
A navigation receiver receives and processes radio signals broadcast by satellites
located within line-of-sight distance, and from this, computes the position of the
receiver within a pre-defined coordinate system. However, for military reasons, the
most accurate parts of these satellite signals are encrypted with codes only known
to military users. Civilian users cannot access the most accurate parts of the satellite
signals, which makes it difficult for civilian users to achieve accurate results.
In addition, there are sources of noise and error that degrade the accuracy of the
satellite signals, and consequently reduce the accuracy of computed values of position.
Such sources include carrier ambiguities, receiver time offsets, and atmospheric effects
on the satellite signals.
[0003] The present invention is directed to increasing the accuracy of estimating the position
of a rover station in view of carrier ambiguities, receiver time offsets, and atmospheric
effects.
SUMMARY OF THE INVENTION
[0004] The present invention relates to a method and apparatus for determining the position
of a receiver (
e.g., rover) with respect to the positions of at least two other receivers (
e.g., base receivers) which are located at known positions. The knowledge of the precise
locations of the at least two other receivers (located at known positions within the
coordinate system) makes it possible to better account for one or all of carrier ambiguities,
receiver time offsets, and atmospheric effects encountered by the rover receiver,
and to thereby increase the accuracy of the estimated receiver position of the rover
(
e.
g., rover position).
[0005] In a first aspect of the present invention, an exemplary apparatus/method comprises
receiving the known locations of a first base station and a second base station, obtaining
a time offset representative of the time difference between the clocks of the first
and second base stations, and obtaining measured satellite data as received by the
rover, the first base station, and the second base station. The measured satellite
data comprises pseudo-range information. The exemplary apparatus/method generates
a first set of residuals of differential navigation equations associated with a set
of measured pseudo-ranges related to a first baseline (R-B1) between the rover and
the first base station. The residuals are related to the measured satellite data received
by the rover station and the first base station, the locations of the satellites,
and the locations of the rover station and the first base station. The exemplary apparatus/method
also generates a second set of residuals of differential navigation equations associated
with a set of measure pseudo-ranges related to a second baseline (R-B2) between the
rover and the second base station. These residuals are related to the measured satellite
data received by the rover station and the second base station, the locations of the
satellites, and the locations of the rover station and the second base station. The
exemplary apparatus/method estimates the rover's location from the first set of residuals,
the second set of residuals, the time offset between the clocks of the first and second
base stations.
[0006] In a second aspect of the present invention, the position information and measured
satellite data from a third base station are received. Also, a time offset representative
of the time difference between the clocks of the first and third base stations is
obtained. Thereafter, the exemplary apparatus/method also generates a third set of
residuals of differential navigation equations associated with a set of measured pseudo-ranges
related to a third baseline (R-B3) between the rover and the third base station, and
estimates the rover's location further with the third set of residuals and the time
offset between the clocks of the first and third base stations.
[0007] In a third aspect of the present invention, which may be applied with any of the
aspects of the present invention described herein, the exemplary apparatus/method
generates the time offset(s) for the base stations from the measured satellite data
of the base stations provided to it.
[0008] In a fourth aspect of the present invention, which may be applied with any of the
aspects of the present invention described herein, the exemplary apparatus/method
obtains measured satellite carrier phase data as received by the rover and the first
base station (the first base line). The exemplary apparatus/method generates a fourth
set of residuals of differential navigation equations associated with a set of measured
carrier phase data related to the first base line, and resolves the cycle ambiguities
in the carrier phase data from the fourth residual and one or more of the first, second,
and third residuals. The resolved cycle ambiguities may take the form of floating
ambiguities, fixed-integer ambiguities, and/or integer ambiguities. The exemplary
apparatus/method estimates the rover's location further with the fourth set of residuals
and the resolved cycle ambiguities associated with the first base line.
[0009] In a fifth aspect of the present invention, which may be applied with any of the
aspects of the present invention described herein, the exemplary apparatus/method
obtains measured satellite carrier phase data as received by the second base station,
and further obtains a set of cycle ambiguities related to a set of satellite phase
measurements associated with the baseline between the first and second base stations
(B1-B2). The exemplary apparatus/method generates a fifth set of residuals of differential
navigation equations associated with a set of measured carrier phase data related
to the second base line between the rover and the second base station (R-B2), and
resolves the cycle ambiguities in the carrier phase data from the fifth residual,
the set of cycle ambiguities associated with the baseline between the first and second
base stations, and one or more of the first, second, third, and fourth residuals.
The resolved cycle ambiguities may take the form of floating ambiguities, fixed-integer
ambiguities, and/or integer ambiguities. The exemplary apparatus/method estimates
the rover's location further with the fifth set of residuals and the resolved cycle
ambiguities associated with the second base line (R-B2).
[0010] In a sixth aspect of the present invention, which may be applied with any of the
aspects of the present invention described herein, the exemplary apparatus/method
receives measured satellite carrier phase data as received by the third base station,
and further obtains a set of cycle ambiguities related to a set of satellite phase
measurements associated with the baseline between the first and third base stations
(B1-B3). The exemplary apparatus/method generates a sixth set of residuals of differential
navigation equations associated with a set of measured carrier phase data related
to the third base line between the rover and the third base station (R-B3), and resolves
the cycle ambiguities in the carrier phase data from the sixth residual, the set of
cycle ambiguities associated with the baseline between the first and third base stations,
and one or more of the first, second, third, fourth, and fifth residuals. The resolved
cycle ambiguities may take the form of floating ambiguities, fixed-integer ambiguities,
and/or integer ambiguities. The exemplary apparatus/method estimates the rover's location
further with the sixth set of residuals and the resolved cycle ambiguities associated
with the third base line (R-B3).
[0011] In a seventh aspect of the present invention, which may be applied with any of the
aspects of the present invention described herein, the exemplary apparatus/method
obtains a first set of first ionosphere delay differentials associated with the satellite
signals received along the base line formed by the first and second base stations,
and generates ionosphere delay corrections to one or more of the above-described first
through sixth residuals from the first set of first ionosphere delay differentials,
the locations of the first and second base stations, and an estimated location of
the rover station. As a further option, the exemplary apparatus/method obtains set
of second ionosphere delay differentials associated with the satellite signals received
along the base line formed by the first and third base stations (or the base line
formed by the second and third base stations), and generates the ionosphere delay
corrections to the one or more of the above-described first through sixth residuals
further from the second set of ionosphere delay differentials and the location of
the third base station.
[0012] In an eight aspect of the present invention, which may be applied to the seventh
and further aspects of the present invention described herein, the exemplary apparatus/method
forms one or more of the first through sixth residuals to account for second order
effects in the ionosphere delay corrections applied to the baselines associated with
the rover, and further generates an estimate of the second order effects.
[0013] In a ninth aspect of the present invention, which may be applied with any of the
aspects of the present invention described herein, the exemplary apparatus/method
generates the time offset representative of the time difference between the clocks
of the first and second base stations, and optionally the time offset representative
of the time difference between the clocks of the first and third base stations. As
a further option, the apparatus/method generates the time offset representative of
the time difference between the clocks of the second and third base stations, and
performs a consistency check of the time offsets.
[0014] In an tenth aspect of the present invention, which may be applied with several of
the aspects of the present invention described herein, the exemplary apparatus/method
generates the resolved cycle ambiguities associated with the baseline between the
first and second base stations (B1-B2), and optionally generates the resolved cycle
ambiguities associated with the baseline between the first and third base stations
(B1-B3). As a further option, the apparatus/method generates the resolved cycle ambiguities
associated with the baseline between the second and third base stations (B2-B3), and
performs a consistency check of the cycle ambiguities associated with the baselines
between the base stations.
[0015] In an eleventh aspect of the present invention, which may be applied with any aspects
of the present invention described herein which account for ionosphere delays, the
exemplary apparatus/method generates the first set of first ionosphere delay differentials,
and optionally the second set of first ionosphere delay differentials. As a further
option, the apparatus/method generates a third set of ionosphere delay differentials
associated with the satellite signals received along the base line formed by the second
and third base stations, and generates therefrom three sets of ionosphere delay differentials
which are self consistent.
[0016] Accordingly, it is an object of the present invention to increase the accuracy of
estimating the rover's position using information from one or more baselines associated
with two or more base stations.
[0017] It is a further object of the present invention to enable the spacing between the
rover and the base stations to increase while maintaining or improving the accuracy
of the estimation of the rover's position.
[0018] These and other objects of the present invention will become apparent to those skilled
in the art from the following detailed description of the invention, the accompanying
drawings, and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019]
FIG. 1 is a perspective view of a rover station (R) and three base stations (B1, B2,
B3) in an exemplary network according to exemplary embodiments of the present invention.
FIG. 2 is a top-plan schematic drawing the rover station (R) and three base stations
(B1, B2, B3) in the exemplary network shown in FIG. 1 according to the present invention.
FIG. 3 is a perspective view of the ionosphere delay differentials to selected exemplary
methods according to the present invention.
FIG. 4 is a top-plan schematic view of a road application where a reduced level of
interpolation of ionosphere delays maybe used according to the present invention.
FIG. 5 is a schematic diagram of an exemplary rover station according to the present
invention.
FIG. 6 is a general flow diagram of embodiments of the present invention.
FIG. 7 is a schematic diagram of an exemplary computer program product according to
the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0020] FIG. 1 is a perspective view of a rover station (R) and three base stations (B1,
B2, B3) in an exemplary network according exemplary embodiments of the present invention,
and FIG. 2 is a top-plan schematic drawing thereof. The present invention pertains
to estimating the position of the rover station with information provided from two
or three of the base stations and with satellite measurements made by the rover station.
Referring to FIG. 1, each station has a receiver that receives the satellite positioning
signals with a satellite antenna (shown as a substantially flat disk). A plurality
of satellites S1-S4 are depicted in FIG.1, with the range between each satellite and
each antenna being depicted by a respective dashed line. In the example shown and
FIG. 1, the Rover station is operated by a human user, and has a positioning pole
for positioning the Rover's satellite antenna over a location whose coordinates are
to be determined. The Rover's satellite antenna is coupled to the receiver's processor,
which may be disposed in the backpack and carried by the user. The user interacts
with the receiver's processor through a keypad/display. The receiver also has a radio
modem (more formally a demodulator) that can receive data from the base stations through
a conventional RF antenna and relay it to the processor. In other embodiments, the
Rover's satellite antenna may be mounted to a vehicle, and the receiver may operate
independently and automatically without the need of a human operator. The present
invention is applicable to these and other physical embodiments.
[0021] The satellite signals comprise carrier signals which are modulated by pseudo-random
binary codes, which are then used to measure the delay relative to local reference
clock or oscillator. These measurements enable one to determine the so-called pseudo-ranges
between the receiver and the satellites. The pseudo-ranges are different from true
ranges (distances) between the receiver and the satellites due to variations in the
time scales of the satellites and receiver and various noise sources. To produce these
time scales, each satellite has its own on-board atomic clock, and the receiver has
its own on-board clock, which usually comprises a quartz crystal. If the number of
satellites is large enough (four or more), then the measured pseudo-ranges can be
processed to determine the user location (
e.g., X, Y, and Z coordinates) and to reconcile the variations in the time scales. Finding
the user location by this process is often referred to as solving a navigational problem
or task.
[0022] More specifically, the GPS system employs a constellation of satellites in orbit
around the earth at an altitude of approximately 26,000 km. Each GPS satellite transmits
microwave radio signals in two frequency bands located around 1575.42 MHz and 1227.6
MHz, referred to as L1 band and L2 band, respectively. The GPS L1-band signal is modulated
by a coarse/acquisition code (C/A) and a precision ranging code (P-code). The L2-band
signal is binary modulated by the P-code. The GPS C/A code is a pseudo-random (PR)
Gold code that is specific to each satellite and is used to identify the source of
a received signal. The P-code is a pseudo-random code signals and is also specific
to each satellite, having a symbol rate which is ten time more than C/A, which reduces
the granularity by a factor of ten. The GPS satellite transmission standards are set
in detail by
the ICD-GPS-200, Revision C, ARINC Research Corporation, 10 October, 1993.
[0023] The satellites of the GLONASS system transmit signals in two frequency bands around
1602 MHz, and around 1246 MHZ, referred to also as L1 band and L2 band, respectively.
The GLONASS L1-band signal is modulated by a pseudo-random C/A code and a pseudo-random
P-code. The L2-band signal is modulated by the P-code. Unlike GPS, in which all of
the satellites transmit on the same nominal frequency, the GLONASS satellites each
transmit at a unique frequency in order to differentiate between the satellites. The
GLONASS L1-band carrier frequency is equal to 1602 MHz +
l*0.5625 MHz, where
l is an integer index ranging between 0 and 24 that identifies the satellites. The
GLONASS L2-band carrier frequency is equal to 1246 MHz +
l*0.4375 MHz. Details of the GLONASS signals maybe found in
GLONASS ICD, Version 4.0, 1998.
[0024] The distance between a receiver and a satellite (called the "receiver-to-satellite
range") is determined by measuring the time that it takes for the signal to pass from
the satellite to the receiver, provided that the position of the satellite is known.
The satellites and receivers have internal clocks that are synchronized to a single
GPS time. For each satellite signal being tracked, the receiver generates a local
version of the satellite's expected PR-code, and then retards that version in time
until the local version correlates
(i.e., matches) with the received satellite signal. Thereafter, the satellite signal is
tracked by advancing or retarding the local version of the PR-code. The carrier phase
of the satellite can also be tracked, which is usually done by tracking the Doppler
shift of the satellite signal. The positions of the satellites are, except for minor
variations, highly predictable as a function of time, and the receiver generally carriers
a model of the satellite's position as a function of GPS time. In theory, by determining
the ranges to three different satellites, the receiver can perform a three-dimensional
triangulation to find its position. But because limitations in the accuracy of the
receiver's clock, the internally generated time is offset somewhat from true GPS time.
Thus, the ranges to at least four different satellites are simultaneously measured
in order to be able to solve for four unknowns, namely the three coordinates of the
position of the receiver location (
e.g., x, y, and z) and an offset of the receiver clock time from the GPS time. The location
is usually performed with respect the defined Cartesian coordinates frame.
[0025] In theory, a GPS receiver can track both the C/A code and the P-code of a satellite.
The C/A code generally provides accuracy to within 20 - 50 meters, and the P-code
generally provides greater accuracy to within 10 meters because of its higher repetition
rate (less granularity) relative to the C/A code. However, knowledge of the P-code
is restricted to military users and not available to civilian users. Nonetheless,
some approaches for tracking P-codes have been developed.
[0026] The desire to guarantee the solution of navigational tasks with accuracy better than
10 meters, and the desire to raise the stability and reliability of measurements,
have led to the development of the mode of "differential navigation ranging," also
called "differential navigation" (DN). In the DN mode, the task of finding the user
position is performed relative to a Base station (Base), the coordinates of which
are known with the high accuracy and precision. The Base station has a navigation
receiver that receives the signals of the satellites and processes them to generate
measurements. The results of these measurements enable one to calculate corrections,
which are then transmitted to a roving GPS receiver, which the user has set up. We
call this GPS receiver the "Rover station," or "Rover receiver." By using these corrections,
the roving GPS receiver gains the ability to compensate for the major part of the
strongly correlated errors in the measured pseudo-ranges, and to substantially improve
the accuracy of the estimate of its position.
[0027] Usually, the Base station is immobile during measurements. The rover station may
be either immobile or mobile. Depending on the navigational tasks to be solved, different
modes of operation may be used in the DN mode. They differ in the way in which the
measurement results are transmitted from the Base to the Rover. In the post-processing
(PP) mode, these results are transmitted as digital recordings and go to the user
after all the measurements have been finished. In the PP mode, the user reconstructs
his or her location for definite moments in the past.
[0028] Another mode is the Real-Time Processing (RTP) mode, and it provides for the positioning
of the Rover receiver just during the measurements. The RTP mode uses a communication
link (such as the radio communication links shown in FIG. 1), through which all the
necessary information is transmitted from the Base to the Rover receiver in digital
form.
[0029] Further improvement of accuracy of differential navigation may be reached by supplementing
the measurements of the pseudoranges with the measurements of the phases of the satellite
carrier signals. If one measures the carrier phase of the signal received from a satellite
in the Base receiver and compares it with the carrier phase of the same satellite
measured in the Rover receiver, one can obtain measurement accuracy to within several
percent of the carrier's wavelength,
i.e., to within several centimeters.
[0030] The practical implementation of those advantages, which might be guaranteed by the
measurement of the carrier phases, runs into the problem of there being ambiguities
in the phase measurements.
[0031] The ambiguities are caused by two factors. First, the difference of distances
ΔD from any satellite to the Base and Rover is usually much greater than the carrier's
wavelength
λ. Therefore, the difference in the phase delays of a carrier signal
Δϕ=ΔD/
λ received by the Base and Rover receivers may substantially exceed one cycle. Second,
it is not possible to measure the integer number of cycles in
Δϕ from the incoming satellite signals; one can only measure the fractional part of
Δϕ. Therefore, it is necessary to determine the integer part of
Δϕ, which is called the "ambiguity". More precisely, we need to determine the set of
all such integer parts for all the satellites being tracked, one integer part for
each satellite. One has to determine this set along with other unknown values, which
include the Rover's coordinates and the variations in the time scales.
[0032] In a general way, the task of generating highly-accurate navigation measurements
may be formulated by defining a set of unknowns and system of relationships between
the unknowns and measured navigation parameters. The vector of unknowns, denoted herein
as
nΣ, include three Rover coordinates (usually along Cartesian axes X, Y, Z) in a given
coordinate system (sometimes time derivatives of coordinates are added too); the variations
of the time scales which is caused by the phase drift of the local main reference
oscillator; and
n integer unknown values associated with the ambiguities of the phase measurements
of the carrier frequencies. The value of
n is determined by the number of different carrier signals being processed, and accordingly
coincides with the number of satellite channels actively functioning in the receiver.
At least one satellite channel is used for each satellite whose broadcast signals
are being received and processed by the receiver. Some satellites broadcast more than
one code-modulated carrier signal, such as a GPS satellite, which broadcasts a carrier
in the L
1 frequency band and a carrier in the L
2 frequency band. If the receiver processes the carrier signals in both of the L
1 and L
2 bands, the number of satellite channels (
n) increases correspondingly.
[0033] Two sets of navigation parameters are measured by the Base and Rover receivers, respectively,
and are used to determine the set of unknowns, which is sometimes called the "state
vector." Each set of navigation parameters includes the pseudo-range of each satellite
to the receiver, and the full (complete) phase of each satellite carrier signal. Each
pseudo-range is obtained by measuring the time delay of a code modulation signal of
the corresponding satellite (C/A code or P-code). The code modulation signal is tracked
by a delay-lock loop (DLL) circuit in each satellite-tracking channel. The full phase
of a satellite's carrier signal is tracked by a phase-lock-loop (PLL) in the corresponding
satellite tracking channel. (The DLL and PLL are, for example, provided by the demodulator
120 of an exemplary rover shown in FIG. 5). An
observation vector is generated as the collection of the measured navigation parameters for specific
(definite) moments of time.
[0034] The relationship between the state vector and the observation vector is defined by
a well-known system of navigation equations. Given an observation vector, the system
of equations may be solved to find the state vector if the number of equations equals
or exceeds the number of unknowns in the state vector. In the latter case, conventional
statistical methods are used to solve the system: the least squares method, the method
of dynamic Kalman filtering, the method of least squares and various modifications
of these methods.
[0035] One method may comprise the following steps. The measured values of the pseudo-ranges
and full phases at specific (definite) moments of time, along with an indication of
the satellites to which these measurements belong to and the time moments of the measurements,
are transmitted from the Base to the Rover (such as through the communication link
or as recordings). Corresponding values are measured in the Rover receiver. The processing
includes the determination of the single differences of the pseudo-ranges and full
phases between the Base and Rover measurements for each satellite. The strongly correlated
errors are largely compensated (
i.e., substantially cancelled) in the single differences. Then, the residuals of the single
differences are calculated by subtraction of calculated values from the measured results.
The processing of residuals allows one to linearize the initial system of navigation
equations (sometimes several subsequent iterations are necessary for that), which
makes possible the use of the well-developed body of mathematics for solving systems
of linear equations. The subsequent iterative solution of the linearized system of
navigation equations is equivalent to the minimization of the sum of squared non-linear
residuals by the Gauss-Newton minimization method. The components of the state vector,
with the
n ambiguities included, are found as a result of the solution. But the calculated values
of the ambiguities are not necessarily integer numbers, and are often floating point
numbers. Because of this, they are called "float ambiguities," or "floating ambiguities,"
at this stage of the solution. To find true values of the integer ambiguities one
uses the procedure of rounding off the float ambiguity vector to the nearest set of
integers. This process is called 'the ambiguity resolution'. After the ambiguity resolution
has been done, is it possible to generate more accurate values of residuals and then,
by solving the system of equation again, to find the coordinate values for the baseline
connecting the Base and Rover, and consequently to more accurately estimate the coordinates
of Rover and the correction to its clock drift.
[0036] There are fractional parts associated with each ambiguity due to the time offset
in the receiver's carrier generator, and as a practical matter, it is more convenient
to include this fractional offset into the floating ambiguities and "integer" ambiguities.
In this case, one additionally solves for the unknown fractional offset of the receiver's
carrier generator, and then resolves the "integer" ambiguities in the form of integers
plus a common fractional part that is related to the time offset of the receiver's
carrier generator. We call these resolved ambiguities "fixed-integer ambiguities"
because, although these ambiguities have fractional parts, the difference between
any two fixed-integer ambiguities for two corresponding satellites measured by the
same pair of receivers is an integer.
[0037] Even with all of the-above described processing to account for clock offsets and
carrier ambiguities, there are additional factors which affect the accuracy of measurements
made with GPS and/or GLONASS signals. As one factor, the trajectory of each satellite
(or its initial data called the ephemeris), is elliptical and is affected by natural
causes such as solar winds. The accuracy of any measurement is dependent upon knowledge
of the position of the satellites at certain time. An estimate of the ephemeris is
calculated on earth for each of the satellites and is periodically uploaded to the
satellite. The position information of a satellite is encoded onto a low frequency
(50 Hz) signal which is modulated on to one of the carrier signals, and transmitted
to the GPS receiver on earth.
[0038] Two additional and important factors that affect the accuracy of measurements made
with GPS and/or GLONASS signals are the effects of the troposphere and ionosphere
on propagation of signals from the satellites to the receivers. The troposphere is
the lower part of the atmosphere and variations in the temperature, pressure, and
humidity lead to spatial variations in the signal propagation. The ionosphere is at
the upper part of the atmosphere and has a slice of ionized gas at the altitude of
around 300 km. The density of ionized particles is sufficiently high to affect the
propagation of electromagnetic signals, and has a spatial variation and a time variation.
The ionosphere effect becomes even more important during years of high solar activity.
These variations in the troposphere and ionosphere introduce variable delays in the
propagation the satellite signals to the receivers. If the base and rover are widely
separated, these delays will be significantly different for the base and rover stations,
and will introduce error into the estimation of the rover's position.
[0039] With that general overview, we now describe the invention in greater detail. For
the sake of simplifying the presentation, and without loss of generality, we assume
"
N" satellites identified by the index
"s", s = 1, ...,
N, and we assume that each receiver can track the satellite's L1 band signal and the
satellites L2 band signal. The receivers extract timing information from the satellite
signals, and report this information a predefined increments
k of time, which we call epochs
k. The time between epochs can be selected by the user, and generally ranges between
0.1 seconds to 2 seconds, with 1 second being typical. The clocks of all of the receivers
are typically accurate to within several milliseconds of the true GPS time, and for
practical purposes the receivers can determined the number
k of the current epoch from their clocks. The following timing information can be extracted
from each satellite
"s" at each epoch "
k" by each receiver "
r":
- 1. The low-frequency (50 Hz) information signal which provides information on the
orbit (position) of the satellites which enables the receiver to determine the satellite's
position.
- 2. the pseudo-range
derived from the L1-band C/A code (or optionally the L1-band P-code for military
users), and having the units of length (e.g., meters [m]);
- 3. the pseudo-range
derived from the L2-band C/A code (or optionally the L2-band P-code for military
users), and having the units of length (e.g., meters [m]);
- 4. the L1-band carrier phase
derived from the L1-band carrier, and typically having the dimensionless units of
cycles (but is sometimes expressed in terms of meters by multiplying the cycles by
the L1-band wavelength λL1,s; and
- 5. the L2-band carrier phase
derived from the L2-band carrier, and typically having the dimensionless units of
cycles (but is sometimes expressed in terms of meters by multiplying the cycles by
the L2-band wavelength λL2,s.
Each of
and
are known as observed quantities, or "observables," because the are measured by the
receiver from the satellite signals. The observables are related to the speed of light
"c," the wavelengths λ
L1,s and λ
L2,s of the L1-band and L2-band carriers of satellite "
s," the frequencies
f L1,s =c/ λ
L1,s and
fL2,s =c/λ
L2,s of the L1-band and L2-band carriers of satellite "
s," various variables that are to be determined, and various noise sources, in the
following manner:
where variables (which are to be determined) are:
is the true range between the satellite "s" and receiver "r" at the epoch "k", having dimension of distance (usually expressed as meters [m]);
is the time offset from true GPS time of the clock of satellite "s" at epoch "k";
- τr,k is the time offset from true GPS time of the clock of receiver "r" at epoch "k";
is the delay due to tropospheric effects between satellite "s" and receiver "r" at
epoch "k";
is the delay due to ionospheric effects between satellite "s" and receiver "r" at
epoch "k" (the full amount of
affects the pseudo-range in the L1-band);
is the integer phase ambiguity in the L1-band observable
is the integer phase ambiguity in the L2-band observable
is the initial phase offset of the L1-band phase tracker of receiver "r"; and
is the initial phase offset of the L2-band phase tracker of receiver "r",
and where various noise sources are:
is the total effect of the noise sources on the pseudo-range measurement at epoch
"k" in receiver "r" when tracking the L1-band C/A-code signal (or P-code signal) of satellite "s";
is the total effect of the noise sources on the pseudo-range measurement at epoch
"k" in receiver "r" when tracking the L2-band C/A-code signal (or P-code signal) of satellite "s";
is the total effect of the noise sources on the carrier-phase measurement at epoch
"k" in receiver "r" when tracking the L1-band carrier of satellite "s"; and
is the total effect of the noise sources on the carrier-phase measurement at epoch
"k" in receiver "r" when tracking the L2-band carrier of satellite "s".
Forms [1A]-[1D] are known as the satellite navigation equations.
[0040] In embodiments of the present invention, we will be forming differences between the
observables of pairs of stations, and differences between instances of the satellite
navigation equations. The vector, or straight line, between a pair of two such stations
is called a baseline. The baselines between all of the stations shown in FIG. 1 are
best seen in the top plan view of FIG. 2. We generally note the difference of an observable
measured by two stations with the prefix notation Δ
q,r, where each of "q" and "r" represents one of the stations B1, B2, B3, and R. For example,
Forms [2A]-[2D] are often referred to as the between-station (or between-receiver)
single differences of the signals of satellite
"s" between stations (receivers) "
r" and "
q". The between station operator Δ
q,r can be applied to the variables and noise sources as well. For example,
and
With this background, we can relate the between-station single differences of the
observables to the differences in the variables as follows:
The difference form of [3A] is generated by forming two instance of form [1A] for
receivers "
r" and "
q", and then subtracting the two instances (the instance for receiver "
q" is subtract from the instance for receiver "
r"). Difference forms [3B], [3C], and [3D], are formed in a similar manner from corresponding
instances of forms [1B], [1C], and [1D], respectively. Forms [3A]-[3D] are the single-differences
of the navigation equations. The benefit of forming the between-station single differences
is that the error term representing the time offset of the satellite clock,
is cancelled out in the differences. We emphasize that the forms [3A]-[3D] can be
applied to each satellite that can be observed by receivers "
q" and "
r." Higher-order differences of the navigation equations, such as the double-differences
of the navigation equations, can be formed and are known to the art. For example,
a common double-difference equation is the difference between two singles-difference
equations associated with a common baseline, but with each single-difference equation
being based on a different satellite. The present invention may also use these higher-order
differences of the navigation equations, although the single differences of the navigation
equations are currently preferred. Each of these difference forms is generically referred
to as a differential navigation equation.
Between Base Station Processing, Part I.
[0041] Because the locations of the base stations are known, and because the locations of
the satellites as a function of epoch time (
k) are also known, the between station differences of each true range
associated with each satellite "
s" can be generated from existing information. If vectors
Xr, Xq, and
Xs represent the locations of receiver "
r", receiver "
q", and satellite
"s", respectively, in a coordinate system (
e.g., Cartesian coordinate system), and the operator ∥·∥ represent the distance operator
in that coordinate system, then
This reduces by one the number of unknowns in forms [3A]-[3D]. In addition, the Goad-Goodman
model may be used to model the difference in troposphere effects (with an error less
than a few percent), and thus the difference
may be estimated based on the positions of the receivers and the satellite (more
specifically, the angles between the receivers and satellites). The noise sources
Δ
q,rnL1,s, Δ
q,rnL2,s, Δ
q,rvL1,s, and Δ
q,rvL2,s can never be known, but they are generally zero-mean and their effect can be reduced
by averaging. Thus, the number of solvable unknowns in forms [3A]-[3D] may be reduced
to the following six: (1) Δ
q,rτk, (2)
(3) Δ
q,rNL1,s, (4) Δ
q,rψL1, (5) Δ
q,rNL2,s (6) Δ
q,rψL2. The first unknown varies with time and is common to all of the satellites being tracked
by receivers
"q" and "r." The second unknown varies with time and is specific to the satellite
"s" being tracked by the pair of receivers
"q" and "r." The third and fifth unknowns are each specific to the satellite "s" being
tracked by the pair of receivers
"q" and "r", and each does not normally vary with time unless a cycle slip occurs in
the receivers phase-lock loop. The forth and sixth unknowns are specific to the pair
of receivers
"q" and
"r," and do not normally vary with time.
[0042] As a practical matter, we note that the third and fourth unknowns are related to
the L1-carrier phase measurement of satellite "
s" and are time-independent (unless a cycle slip occurs). In theory, these unknowns
can be represented as a combined unknown Δ
q,rN̂L1,s = Δ
q,rNL1,s + Δ
q,rψL1, which we call the between-station "fixed-integer ambiguity" for the L1 carrier of
satellite "s," as measured at stations
"q" and "
r." We call these resolved ambiguities "fixed-integer ambiguities" because, although
these ambiguities have fractional parts, the difference between any two fixed-integer
ambiguities for two corresponding satellites measured by the same pair of receivers
is an integer. In a similar manner, the fifth and sixth unknowns are related to the
L2-carrier phase measurement of satellite "
s" and are time-independent (unless a cycle slip occurs); they can be represented as
a combined unknown Δ
q,rN̂L2,s = Δ
q,rNL2,s + Δ
q,rψL2, which we call the between-station "fixed-integer ambiguity" for the L2 carrier of
satellite "s", as measured at stations
"q" and
"r"
[0043] As a further practical matter, one first generates floating point versions of the
fixed-integer ambiguities, and then applies a discretization process to the floating
point version to generate the fixed-integer ambiguities. We call these versions the
floating-point ambiguities, and denote them as Δ
q,rNL1,s ≅ Δ
q,rNL1,s + Δ
q,rψL1 and Δ
q,rNL2,s ≅ Δ
q,rNL2,s + Δ
q,rψL2.
[0044] Thus, the solvable unknowns for each instance of form [3A]-[3D] can be reduced to
four: (1) Δ
q,rτk, (2)
(3) Δ
q,rN̂L1,s(Δ
q,rNL1,s)
, and (4) Δ
q,rN̂L2,s (Δ
q,rNL2,s)
. The first unknown is common to all the satellites being tracked by the pair of receivers
"q" and
"r," whereas the last three are specific to the satellite "
s." The first two unknowns vary with time, whereas the last two are time invariant
(unless a cycle slip occurs). For the base stations, the known values of forms [3A]
- [3D] can be represented as:
Forms [4A]-[4D] comprise the known terms of the single-differences of the navigation
equations, and we call them the "residuals" of the single differences, or more generally
the "residuals of a set of differential navigation equations". The magnitude of each
residual is generally less than the magnitudes of one or more of the known terms that
forms the residual.
[0046] All of the residuals, forms, known values, and unknown variables are real-valued.
The estimation process usually includes instances of forms [5A]-[5D] for several satellites,
and for several epochs of time.
[0047] As one aspect of the present invention, one or more of the unknown variables for
several satellites are estimated for at least two base stations, and preferably for
at least three base stations by a process that is performed at the rover. Using the
numbers 1, 2, and 3 to represent the base stations B1, B2, and B3, respectively, in
the difference operator "Δ
q,r", the estimated values of the between-base station unknowns for each satellite "
s" at each epoch "
k" are:
An exemplary estimation process is outlined in a section below entitled
"Between Base Station Processing, Part II." As one option, the estimation process may break down the fixed integer ambiguities
into their components as follows:
In some applications of the present invention where lower estimate accuracy is acceptable,
floating-point ambiguities may be used in place of the fixed-integer ambiguities,
and the following set of between-base station unknowns may be generated:
Between Rover and Base Station Processing.
[0048] The processing of differences between the rover station and any one of the base stations
is more complex because we do not know the position of the rover beforehand.
[0049] Thus, the term
is not exactly known. However, given an initial estimated value of the rover's location,
which we will denote as
X0 and which can be generated from the 50 Hz information signals by means known to the
art, we can generate an initial range estimate between satellite "s" and the rover,
which we denote as
and we can generate a linearized approximation of the term as follows, where we use
r=0 to denote the rover and use q to generally indicate any one of the base stations:
where
δXk is the vector difference between the actual location
X0 of the Rover and the initial estimated location
X0 (
X0 =
X0 +
δXk), where
is a row vector comprised of the partial derivatives of the distance form
with respect to the rover location
X0, as evaluated at
X0, and where
has been used as a shorthand notation for
Formally, row vector
is expressed as:
The values of
depend upon the satellite location, which changes with each time moment "
k," and upon the initial location
X0 of the Rover, which may be periodically updated, particularly if the Rover is moving.
The row vectors
for all of the satellites may be collected together as a single
s-by-3 matrix, which we denote as
Ak. Matrix
Ak is commonly known as the Jacobian matrix, the geometry matrix, and the matrix of
directional cosines. It is commonly computed in the art and described in many tutorial
textbooks on global positioning. The reader unfamiliar with the GPS is directed to
these tutorial texts for more detailed explanations of how matrix
Ak (which is oftentimes referred to matrix
H or matrix
G by these texts) is generated.
[0051] The solvable unknowns for form [9] includes
δXk, as well as Δ
q,0τk, Δ
q,0N̂L1,s, and Δ
q,0N̂L2,s. As described below in greater detail, estimation processes for these unknowns generally
include instances of forms [9A]-[9D] for several satellites, and for several epochs
of time.
[0052] While the presentation of this section has been made with respect to a specific rover
station (0), it may be appreciated that the discussion and above forms generally apply
to any pair of receivers (q, r), where "r" substitutes for "0" in the above.
Development of the Present Invention
[0053] As part of making their invention, the inventors have recognized that the base station
time-offset unknowns, when accurately estimated, should satisfy the following relationship:
An underlying meaning of this relationship can be seen by noting that Δ
3,1τk = -Δ
1,3τk, and by rewriting the relationship in the equivalent form of Δ
2,1τk + Δ
3,2τk + Δ
1,3τk = 0. That is, the sum of the time offsets around a loop of base stations is equal
to zero. The other unknowns, when accurately estimated, should satisfy the following
similar relationships:
As a further part of making their invention, the inventors have recognized that the
above relationships [10A]-[10J] should be satisfied by any set of three receivers,
including sets where one of the receivers is the receiver of the rover station. We
illustrate this point by replacing station B3 (3) with the rover station, which we
will identify by the subscript number "0":
Still further, the inventors have recognized that relationships [10] and [11] can
be generalized to apply to any loop of four or more receivers. Nonetheless, we provide
exemplary embodiments of the present invention using loops of three receivers in order
to simplify the presentation of the invention.
[0054] According to general aspects of the present invention, the position of the Rover
is estimated by forming a primary baseline between the Rover and one of the base stations,
usually the closest base station, and then forming one or more secondary baselines
from the Rover to other base stations. Then, one or more of the above relationships
are applied to the configuration of stations to relate the measured data associated
with the secondary baseline(s) with the measured data associated primary baseline
using one or more of the unknowns associated with the baselines between base stations
through forms [11]. To simplify the presentation of the present invention, and without
loss of generality, we will use base station B1 to form the primary baseline with
the Rover, and we use base stations B2 and B3 to form the secondary baselines with
the Rover. Varying amounts measured data from the secondary baselines may be related
with the primary baseline. In general, the greater amount of information so related
increases the accuracy of the estimated position of the rover, and/or enables a greater
spacing between base stations.
First General Group of Embodiments
[0055] In a first exemplary embodiment, the measured pseudo-range data from the secondary
baselines are related with the measured pseudo-range data of the primary baseline.
At first, only the L1-band data is used (forms [4A], [5A], [8A], and [9A]). We take
the case where the distances between the stations are small enough that the difference
terms associated with the ionosphere terms
are negligible. For the primary baseline, forms [8A] and [9A] reduce to:
For the secondary baseline to the second base station, we have:
For the secondary baseline to the third base station, we have:
The terms in forms [12A], [14A], and [16A] are the residuals of differential navigation
equations and are known. The unknowns are contained in right-hand sides of forms [13A],
[15A], and [17A]. There are a total of six solvable unknowns: Δ
1,0τk, Δ
2,0τk, Δ
3,0τk, and the three components of
δXk. However, using form [11A], Δ
2,0τk may be related to Δ
0,1τk through the estimated base-station time offset Δ
2,1τk as follows: Δ
2,0τk = Δ
2,1τk-Δ
0,1τk=Δ
2,1τk+Δ
1,0τk. In a similar manner, Δ
3,0τk may be related to Δ
0,1τk through the estimated base-station time offset Δ
3,1τk as follows: Δ
3,0τk = Δ
3,1τk-Δ
0,1τk = Δ
3,1τk+Δ
1,0τk. These two forms reduce the number of true solvable unknowns to four, and the following
modified set of forms may be used to estimate the true solvable unknowns:
As an equivalent, one may view forms Δ
2,0τk = Δ
2,1τk + Δ
1,0τk and Δ
3,0τk = Δ
3,1τk + Δ
1,0τk as increasing the total number of forms by two, and may then estimate the six unknowns
the expanded form set:
The rover's location (
X0 = X0 +
δXk) may be estimated from each of the above form sets using any one of several know
methods. Here, we demonstrate estimating the rover's location with a least squares
fitting approach based on the first form set. After generating the residuals
for N satellites (s=1 to s=N) for the baseline between the rover and the first base
station (R-B1), we collect them together into a first vector:
We do the same for the other two baselines, but modify their residuals according
to the between-base station time offsets
cΔ
2,1τk and
cΔ
3,1τk :
where the superscript" "*" is used to indicate the modification. The noise terms
can be similarly grouped as:
and
The first form set of [13A], [15A*] and [17A*] may then be written in matrix form
as:
The solvable unknowns
may be estimated by a least squares process as follows:
where:
and where
Cn,k is a 3N-by-3N covariance matrix for the noise terms
and
The generation of covariance matrix
Cn,k is well known to the GPS art and described in the technical and patent literature
(see for example
U.S. patent No. 6,268,824, where the covariance matrices are denoted as matrices R), and a description thereof
is not needed for one of ordinary skill in the GPS art to make and use the present
invention. (In a subsequent section, we describe an estimation process that we prefer
to use, and which may be applied to these embodiments.)
[0056] For the reader not familiar with the GPS art, we briefly note that matrix
Cn,k generally comprises a diagonal matrix, with each diagonal element being related to
the noise sources in the two receivers that define the baseline (in this case the
rover and one of the base stations). A covariance factor is usually associated with
each satellite signal received by each receiver, and this covariance factor is usually
related to the signal-to-noise ratio of the signal (as received by the receiver) and
the elevation angle of the satellite (the multipath error has a strong correlation
with the elevation angle). Each diagonal entry of matrix
Cn,k usually comprises an addition of the two covariance factors associated with the two
receivers which contributed to the underlying noise quantity,
e.g., base station B1 and the rover for noise quantity
For more details and information on the generation of the covariance matrices, the
reader is direct to
A. Leick, GPS Satellite Surveying, John Wiley & Sons, (1995). Matrix
is known as the observation matrix, and it relates the solvable unknowns to the residuals.
The solvable unknowns may also be estimated by other processes, such as various Kalman
filtering processes.
[0057] The above may be carried out by omitting the rows related to one of the secondary
base stations B2 and B3, such as the last N rows associated with the third base station.
The above may also be carried out by adding rows related to a fourth base station
(and even more base stations).
[0058] The second form set comprising [13A], [15A], [17A], [11A*], and [11A**] may be written
as:
and the solvable unknowns may similarly be estimated by various least squares processes,
and Kalman filtering processes. The observation matrix in the above form is denoted
as
[0059] Thus, the above exemplary embodiments provide methods of estimating the location
of the rover station (R) with the use of a first base station (B1) a second base station
(B2), and optionally a third base station (B3) or more base stations. In summary,
the locations of the base stations were obtained, and one of the base stations (e.g.,
B1) was selected to form a primary baseline with the Rover station. We refer to this
base station as the primary base station, and the other base stations as the secondary
base stations. Additionally, for each of the secondary base stations, the time offset
representative of the time difference between the clocks of the primary station and
secondary base station is obtained. Also, measured satellite data as received by the
rover, the primary base station, and the secondary base station(s) is obtained. From
this, the set of residuals
associated with the primary baseline (R-B1) is generated, and is related to the measured
satellite data received by the rover station and the first base station, the locations
of the satellites, and the locations of the rover station and the first base station.
Similarly, the set(s) of residuals
etc. associated with the secondary baseline(s) are generated, each set of residuals related
to the measured satellite data received by the rover station and the secondary base
station, the locations of the satellites, and the locations of the rover station and
the secondary base station. Thereafter, the rover's location is estimated from the
above sets of residuals, the time offset between the clocks of the base stations,
and typically an observation matrix.
[0061] One might envision a different approach whereby the Rover's position is estimated
by using each of the three baselines separately to generate three separate estimates
of the Rover's location, and then averaging the three separate estimates to generate
a final estimate. However, the present invention provides more accurate results than
this possible approach because the present invention uses the additional information
provided by forms [11] (specifically, [11A], [11A*] and [11A**]), which correlates
the values of the unknowns associated with the baselines. The achievement of more
accurate results by the present invention is also true for the embodiments described
below.
Second General Group of Embodiments
[0062] The second group of embodiments builds upon the first group of embodiments by generating
and utilizing the residuals derived from the phase measurements at the receivers.
We take the case where the distances between the stations are small enough that the
difference terms associated with the ionosphere terms
are negligible. In later embodiments, we will take these ionosphere terms into account.
With this assumption, forms [8C], [9C], [8D], and [9D] for the primary baseline become
the following forms [12C], [13C], [12D], and [13D], respectively:
For the secondary baseline to the second base station, we have:
For the secondary baseline to the third base station, we have:
The terms in forms [12C, D], [14C, D], and [16C, D] are the residuals of the differential
navigation equations and are known. The unknowns are contained on the right-hand sides
of forms [13C, D], [15C, D], and [17C, D]. For
N satellites, there are
6*N equations and a total of (6+ 6*
N) solvable unknowns: Δ
1,0τk, Δ
2,0τk Δ
3,0τk, the three components of
δXk, and N instances of each of Δ
1,0N̂L1,s, Δ
2,0N̂L1,s, Δ
3,0N̂L1,s, Δ
1,0N̂L2,s, Δ
2,0N̂L2,s, and Δ
3,0N̂L2,s, for
s = 1 to
s = N satellites. However, using forms [11A], [11C], and [11D], the number of unknowns
may be reduced to 4+2*
N. As we saw above, Δ
2,0τk, may be related to Δ
0,1τk through the estimated base-station time offset Δ
2,1τk using form [11A] as follows: Δ
2,0τk = Δ
2,1τk - Δ
0,1τk = Δ
2,1τk + Δ
1,0τk. In a similar manner, Δ
3,0τk was related to Δ
0,1τk through the estimated base-station time offset Δ
3,1τk as follows: Δ
3,0τk = Δ
3,1τk - Δ
0,1τk = Δ
3,1τk + Δ
1,0τk. Form [11C] may be used to related each of the L1 band ambiguities of the secondary
baselines to the primary baseline as follows:
Similarly, Form [11D] may be used to relate each of the L2 band ambiguities of the
secondary baselines to the primary baseline as follows:
Forms [15C] and [15D] for the second base station B2 may then be modified as follows:
Forms [17C] and [17D] for the third base station B3 may be similarly modified:
Similar to form [18
+], forms [13C, D] and modified forms [15C*, D*] and [17C*, D*] can be written in matrix
form:
where:
is an N x1 column vector of the L1-band phase residuals
associated with the primary baseline,
is an N x 1 column vector of the modified L1-band phase residuals
associated with the secondary baseline between the rover and base station B2,
is an N x 1 column vector of the modified L1-band phase residuals
associated with the secondary baseline between the rover and base station B3,
is an N x 1 column vector of the L2-band phase residuals
associated with the primary baseline,
is an N x 1 column vector of the modified L2-band phase residuals
associated with the secondary baseline between the rover and base station B2,
is an N x 1 column vector of the modified L2-band phase residuals
associated with the secondary baseline between the rover and base station B3,
- Ak is the derivative matrix previously described,
- ΛL1 is a diagonal matrix of the carrier wavelengths of the satellites in the L1-band,
and
is its inverse matrix,
- ΛL2 is a diagonal matrix of the carrier wavelengths of the satellites in the L2-band,
and
is its inverse matrix,
- fL1 is a column vector of the carrier frequencies of the satellites in the L1-band, where
where c is the speed of light and 1 is a column vector of 1's,
- fL2 is a column vector of the carrier frequencies of the satellites in the L2-band, where
- INxN is an N x N identity matrix, and
- 0NxN is an N x N matrix of zeros.
The solvable unknowns [
δXk, Δ
1,0τk, Δ
1,0N̂
L1, Δ
2,0N̂
L2]
T may be estimated by applying a number of processes to the combination of forms [21]
and [18+]. Further below, in a subsequent section, we described a preferred process
that can be used on the combination of forms [21] and [18+]. Here, we describe how
a least squares process maybe applied to combined forms of [18+] and [21].
[0063] To combine form [21] with [18+], we rewrite form [22] to substitute
c·Δ
1,0τk for Δ
1,0τk as one of the unknowns, using the facts that
and
This facilitates the combination of forms [18+] and [22] as:
A least squares process is applied to form [23] to generate the floating ambiguities
over several epochs, and the floating ambiguities are averaged to generate a estimate
of the floating ambiguities. For each epoch, the following may be generated:
where
is the observation matrix of form [23] (the matrix which is multiplying the solvable
unknowns in form [23]), and where different covariance matrixes
and
are used for the L1-band and L2-band data since the magnitudes and variances of the
noise sources associated with the phase measurements are different from those of the
noise sources associated with the pseudorange measurements. Also, the least squares
method normally produces the floating ambiguities Δ
1,0N
L1, Δ
1,0N
L2 rather than the fixed-integer ambiguities Δ
1,0N̂
L1, Δ
1,0N̂
L2. In practice, the least squares process is applied over many epochs, and the computed
floating ambiguities are averaged to generate a final estimate of the floating ambiguities.
Several averaging processes are described in
U.S. patent No. 6,268,82, and may be used. After generating a suitable set of floating ambiguities, a conventional
method of generating the fixed-integer ambiguities or the integer ambiguities may
take place.
[0064] With the fixed-integer ambiguities estimated, the unknowns
δXk and
c·Δ
1,0τ
k may be estimated by substituting the estimated values of Δ
1,0N̂
L1 and Δ
1,0N̂
L2 into form [23], and moving these terms to the left-hand side with the residuals to
provide form [24]:
We consider the left-hand side of form [24] to be a plurality of sets of residuals
since each comprises the known quantities of differential navigation equations. A
second least squares process may then be applied based on form [24] to estimate the
unknowns
δXk and
c·Δ
1,0τk as follows:
where
is the observation matrix of form [24] (the matrix which is multiplying the solvable
unknowns in form [24]). In form [25], the floating ambiguities may be used in place
of the fixed-integer ambiguities. However, lower accuracy generally results, although
the estimation speed is increased since the step of generating the fix-integer ambiguities
from the floating ambiguities may be omitted.
[0065] With large amount of measurement data afforded by the present invention, various
residuals may be omitted from use in the estimation process. For example, we may only
work with L1-band data of all three stations and only use the residuals associated
with this data. We may also only work with data and residuals from two base stations
(the primary baseline and one secondary baseline). For applications needing lower
accuracy, we may work with the phase and pseudorange data of the primary baseline
(R-B1) and just the pseudorange data or phase data of one of the secondary baselines.
Also, one can undertake an analysis of the satellite constellation and select the
satellites which should provide the highest accuracy, using the pseudo-range and phase
data from the L1- and L2- bands. Finally, while we have illustrated the invention
with the single-difference navigation equations, it may be appreciated that higher-order
differences of the navigation equations may be used. Such higher-order differences
have known quantities (which form the residuals) and similar unknowns to be solved
for, which can be solved by the above-described methods.
[0066] Thus, the above exemplary embodiments from the second group of embodiments provide
methods of estimating the location of the rover station (R) with the use of a first
base station (B1) a second base station (B2), and optionally a third base station
(B3) or more base stations. As a summary of an exemplary embodiment of the second
group, the locations of the base stations were obtained, and one of the base stations
(e.g., B1) was selected to form a primary baseline with the Rover station. Additionally,
for each of the secondary base stations, the time offset representative of the time
difference between the clocks of the primary and secondary base stations is obtained,
and a set of satellite-phase cycle ambiguities related to the baseline between the
secondary and primary base stations is obtained for both of the frequency bands. Also,
measured satellite data as received by the rover, the primary base station, and the
secondary base station(s) is obtained. From this, the sets of residuals
and
of differential navigation equations associated with the primary baseline (R-B1)
are generated, and are related to the measured satellite data received by the rover
station and the first base station, the locations of the satellites, and the locations
of the rover station and the first base station. Similar set(s) of residuals associated
with the secondary baseline(s) are generated, each set of residuals related to the
measured satellite data received by the rover station and the secondary base station,
the locations of the satellites, and the locations of the rover station and the secondary
base station. Thereafter, the rover's location is estimated from the above sets of
residuals, the time offset between the clocks of the base stations, the sets of satellite-phase
cycle ambiguities related to the baseline between the primary base station and the
secondary base stations, and typically an observation matrix.
Third Group of Embodiments
[0067] In the above embodiments, the ionosphere delays were assumed to equally affect the
rover and base stations, and the between-station differences were neglected. When
the base stations and rover are separated by large distances, better accuracy may
be obtained by taking into account the ionosphere delays. This can be done in a number
of ways according to the present invention. FIG. 3 provides a representation of the
ionosphere delays of one satellite "s" at the base and rover stations. Shown is a
3-d Cartesian system having two planar axes, north (n) and east (e), to represent
the terrain on which the stations are located, and a vertical axis to represent the
ionosphere delays of a satellite "s" as a function of the terrain. The ionosphere
delay will be different for each satellite. The locations of the rover station R and
three base stations B1, B2, and B3 are indicated in the north-east plane of the figure.
The ionosphere delays for each of these stations are indicated as
and
respectively. The preferred embodiments of the processing of the base station data,
which is more fully described below, generates estimates for the between base stations
differences in the ionosphere delays
and
which we call ionosphere delay differentials. From two of these differentials, an
estimate for the ionosphere delay between the rover and any of the base stations can
be generated. Here, we are most interested in the difference
associated with the primary baseline, the one between the rover and the first base
station.
[0068] The first approach is to generate an estimate
of
based on an interpolation of two of the known ionosphere delay differentials (
) onto the known approximate location of the rover. Here, we use
and
in the following interpolation:
where
α and
β are interpolation constants. The interpolation constants are determined as follows.
Let
X1, X2, and
X3 be three-dimensional vectors which represent the positions of base stations B1, B2,
and B3, respectively. Let
X0,k represent the approximate estimated position of the rover at the "k" epoch. Furthermore,
let the notation {
X}
n denote the north component of a position vector X or a difference vector X of positions,
and the notation
{X}e denote the east component of a position vector X or a difference vector of positions
X. We can then write the north and east components of the position differences {
X0,k-X1}
n and
{X0,k-X1}
e as:
There are two equations in the two unknowns
α and
β, which can be readily solved for
α and
β. When
X0,k is within the triangle formed by the base stations, both of
α and
β are greater than zero, and their sum is equal or less than one.
[0069] Because
X0,k is not necessarily at the exact position of the rover, the estimate
will not necessarily be equal to the true value
In addition, the ionosphere delay does not always vary in a linear manner over the
terrain, and often has second order variations with respect to the east and north
directions, which are not modeled well by forms [26] and [27]. We model the difference
between
and
caused by these effects by the unknown quantity
and thus we can write:
We can also relate
to
as follows:
which is graphically shown in FIG. 3.
[0070] With form [28], estimates for ionosphere differentials on the secondary baselines
and
can be generated using form [11B]
as follows:
[0071] In composing forms [12] - [17], we neglected the ionosphere delays. In the third
group of embodiments, we add the ionosphere delay terms to these forms. By comparing
the general forms [9A-D] to the specific forms [13A-D], [15A-D], and [17A-D], we can
generate augmented forms [12]-[17] as follows:
The primary baseline -
The secondary baseline to the second base station B2-
The secondary baseline to the third base station B3-
This set of forms comprises N additional solvable unknowns, as present in the vector
δ1,0Ik, which have been incorporated into forms [13'], [15'], and [17']. Also, the rough
ionosphere approximation
Δ1,0Ĩk has been incorporated into forms [12'], [14], and [16']. Finally, the between-base-station
data
Δ2,1Ik has been incorporated into forms [14'], and the between-base-station data
Δ3,1Ik has been incorporated into forms [16'].
[0072] The above-described processes of estimating the floating ambiguities and thereafter
estimating the rover position can be expanded to include the unknowns
δ1,0Ik. For lower accuracy, the unknowns
δ1,0Ik may be omitted from the above forms [13'], [15'], and [17']. However, approximate
information on the ionosphere delays is incorporated into forms [12'], [14'], and
[16'].
Embodiment Implementations
[0073] Having thus described three general groups of embodiments, we now describe an exemplary
rover station 100 in FIG. 5 that may be used to implement any of the above-described
embodiments. Description of rover station 100 is provided in conjunction with a flow
diagram shown in FIG. 6. Referring to FIG. 5, rover 100 comprises a GPS antenna 101
for receiving navigation satellite signals, and RF antenna 102 for receiving information
from the base stations, a main processor 110, an instruction memory 112 and data memory
114 for processor 110, and a keyboard/display 115 for interfacing with a human user.
Memories 112 and 114 may be separate, or difference sections of the same memory bank.
Rover 100 further comprises a satellite-signal demodulator 120 for generating the
navigation data
and
for each epoch
k from the signals received by GPS antenna 101, which is provided to processor 110.
Rover 100 also comprises a base-station information demodulator 130 that receives
information signals from the base stations by way of RF antenna 102. Demodulators
120 and 130 may be of any conventional design. The information received by demodulator
130 includes the positions (X
1, X
2, X
3) of the base stations, the satellite-navigational data (e.g.,
k,
and
r =1,2,3) received by each base station at each epoch
k, and the between-base station unknowns (e.g., Δ
r,q,τk, Δ
r,qNL1,s, Δ
r,qψL1, etc., {r,q} = {1,2},{2,3},{3,1},). Each set of information maybe transmitted on a respective
frequency channel. The between-base station unknowns may be generated by the first
base station B1, and thereafter transmitted to the rover by the first base station.
The first base station may receive the satellite-navigation data from the other base
stations in order to compute the between-base station unknowns. Methods of generating
the between-base station unknowns are described below in greater detail in the section
entitled
Between Base Station Processing, Part II. As another approach, the between the station unknowns may be generated by rover 100
locally by a between-base station processor 140, which receives the positions of the
base stations and their satellite navigation data from base station information to
modulator 130. Processor 140 may implement the same methods described in greater detail
in the below section entitled
Between Base Station Processing, Part II. In addition, processor 140 may comprise its own instruction and data memory, or may
be implemented as part of main processor 110, such as by being implemented as a sub-process
executed by main processor 110.
[0074] Main processor 110 may be configured to implement any and above described embodiments
by the instructions stored in instruction memory 112. We describe implementation of
these embodiments with respect to FIG. 6, where certain of the steps may be omitted
when not needed by a particular embodiment. In step 202, the locations X
1, X
2, X
3 of the base stations B1, B2, B3 are received by base-station information modulator
130 and conveyed to main processor 110. These locations, and the location of the rover
station, are measured at the phase centers of the GPS antennas. Thus, RF antenna 102
and demodulator 130 provides means for receiving the locations of the first base station
and the second base station. Also in step 202, main processor 110 generates an initial
estimated location for rover 100, which is relatively course. This may be the center
of the triangle formed by the base stations, or may be derived from a conventional
single point GPS measurements (as opposed to a differential GPS measurement), or maybe
generated by other means. The means for performing this step is provided by main processor
110 under the direction of an instruction set stored in memory 112.
[0075] In step 204, one of the base stations is selected as a primary base station (B1)
to form a primary baseline with the Rover station. The selection may be arbitrary,
or may be based upon which base station is the closest to the initial estimated location
of the Rover. The other base stations are secondary base stations and form secondary
baselines with the rover. The means for performing this step may be provided by the
human user, as prompted by main processor 100 through keypad/display 115, or may be
provided directly by main processor 110 under the direction of an instruction set
stored in memory 112.
[0076] In step 206, main processor 110 is provided with the measured satellite-navigation
data (e.g.,
and
) as received by the rover (r=0), the primary base station(r=1), and the secondary
base station(s) (r=2,3) at one or more time moments
k (epochs). The data is provided by the modulators 120 (for the Rover data) and 130
(for the base station data). Although these sets of data for each epoch k may be received
at slightly different times (because the base stations are at different distances
from the Rover), the data sets are time-stamped with the epoch identifier (which is
conventional practice), and can be stored in a synchronized queue until all the data
sets for the epoch are received. Also during this step, main processor 110 determines
the positions of the satellites for these time moments from orbital predictions, and
generate the computed ranges of the satellites to the rover and base stations based
on the positions of the satellites and the stations. The means for performing this
step is provided by main processor 110 under the direction of an instruction set stored
in memory 112, with the computed information being stored in data memory 114.
[0077] In step 208, for each secondary base station, Rover 100 obtains a time offset representative
of the time difference between the clocks of the primary and secondary base station
(e.g., Δ
2,1τk, Δ
3,1τk) at the time moments
k. Rover 100 may obtain this information by directly receiving it from the primary
base station B1 by way of demodulator 130, or may obtain at this information by using
between-base station processor 140 to generate it, as indicated above. Either of these
approaches provides the means for obtaining these time differences. As used herein,
the term "obtain" encompasses both the receiving of the information from an outside
source (e.g., the primary base station) and the generating of the information locally
by processor 140.
[0078] The next step 210 is optional, depending upon the embodiment being implemented. In
this step, rover 100 obtains, for each secondary base station, a set of satellite-phase
cycle ambiguities related to the baseline between the secondary and primary base stations
for one or more of the frequency bands (e.g., L1 and L2) at the time moments
k. These ambiguities may be in floating form (e.g, Δ
2,1NL1,s, NΔ
2,1NL2,s, Δ
3,1NL1,s, Δ
3,1NL2,s), fixed-integer form (e.g, Δ
2,1N̂L1,s, Δ
2,1N̂L2,s, Δ
3,1N̂L1,s, Δ
3,1N̂L2,s) or integer plus fractional phase form (e.g., Δ
2,1N
L1,s, Δ
2,1ΨL1; Δ
2,1NL2,s, Δ
2,1ψL2; Δ
3,1NL1,s, Δ
3,1ψL1; Δ
3,1NL2,s, Δ
3,1ψL2). Rover 100 may obtain this information by directly receiving it from the primary
base station B1 by way of demodulator 130, or may obtain at this information by using
between-base station processor 140 to generate it, as indicated above. Either of these
approaches provides the means for obtaining this information. As used herein, the
term "obtain" encompasses both the receiving of the information from an outside source
(e.g., the primary base station) and the generating the information locally with processor
140.
[0079] In step 212, which is optional depending upon the embodiment, main processor 110
generates tropospheric difference terms
at the time moments
k, which are to be used in the residuals. In the step, main processor 110 also generates
the observation matrices for each time moment
k. The means for performing this step is provided by main processor 110 under the direction
of an instruction set stored in memory 112, with the difference terms being stored
in data memory 114.
[0080] In step 214, main processor 110 generates the sets of residuals of the single-difference
navigation equations (e.g.,
and
) associated with the primary baseline (R-B1) at the time moments
k, and generates the sets of residuals of the single-difference navigation equations
associated with the secondary baseline(s) (R-B2, R-B3) at the time moments k. The
forms for generating these residuals were described above, and depend upon the embodiment
being implemented. The means for generating the residuals is provided by main processor
110 under the direction of an instruction set stored in memory 112, with the residuals
being stored in data memory 114.
[0081] As an optional step 216, main processor 110 generates ionosphere corrections and
adds corrections to the residuals. The means for performing this step is provided
by main processor 110 under the direction of an instruction set stored in memory 112,
with the corrections being stored in data memory 114.
[0082] Finally, in step 218, main processor 110 estimates estimate the rover's location
at the one or more time moments
k from the sets of residuals, the time offset between the clocks of the base stations,
the sets of satellite-phase cycle ambiguities related to the baseline between the
primary base station and the secondary base stations (optional), and an observation
matrix. The estimation may be done by the previously-described methods. The means
for performing this estimation step is provided by main processor 110 under the direction
of an instruction set stored in memory 112, with the computed information being stored
in data memory 114.
[0083] Keypad/display 115 may be used to receive an instruction from the human user to commence
an estimation of the position of the Rover, and to provide an indication of the estimated
position of the Rover to the user. For some applications, it may be appreciated that
human and interaction is not required and that the keyboard/display would be replaced
by another interface component, as needed by the application.
Preferred Floating Ambiguity Resolution Process
[0084] We demonstrate the preferred floating ambiguity resolution process using forms [12']
-[17'] above. It may be appreciated that the other previously-described embodiments
of the present invention may use also this floating ambiguity resolution process by
simply omitting forms and/or terms of forms from the process. The general view of
the preferred ambiguity resolution process is to reduce the value of the following
form during a series of epochs:
In form
FΣ,
Δ1,0Nk represent the combined vector of current estimates of floating ambiguities:
Δ1,0Nk = [
Δ1,0NL1,
Δ1,0NkL2], and the following are used for the cases of
and
We have also broken down the weighting matrices
etc., as follows:
etc. All of the other terms used above have been previously described with the exception
of covariance matrix
σ1,0 and matrix
D. The between station ionosphere delay, generally denoted here as
usually follows the Gauss-Markov time model:
where
τe is the time between successive epochs [sec],
τI is the ionosphere model correlation time [sec], Δ
q,rε
k is white noise with the zero mean value and the variance of-
where
where,
α ∈ [1,5] is a scaling parameter depending on the solar activity. Covariance matrix
σ1,0 is a diagonal matrix of all the individual values
and where the inverse square [
σ1,0]
-2 of the covariance matrix is a diagonal matrix of the inverse squares
of the individual values
Since this process is only accounting for the second order effects in the ionosphere
delay differentials (rather than the full amount), the value of
α is generally 2 to 3 times smaller than the value used in a single baseline ambiguity
resolution process which accounts for the full amount.
[0085] In form [31], the term
is a cost function which effectively averages the floating ambiguities over several
epochs by introducing a penalty if the set of estimated floating ambiguities
Δ1,0N̅k at the k-th epoch is too far different from the previous estimated set. Δ
1,0N
k-1. With each successive epoch, the weighting matrix
Dk-1 is generally made to be more convex. The second term of
FΣ generates the weighted sum of the squared residuals of forms [13A], [15A'], and [17A'].
In a similar manner, the third term of
FΣ generates the weighted sum of the squared residuals of forms [13B'], [15B'], and
[17B'], the fourth term generates the weighted sum of the squared residuals of forms
[13C'], [15C'], and [17C'], and the fifth term generates the weighted sum of the squared
residuals of forms [13D'], [15D'], and [17D']. The residual of each of the above forms
of [13'], [15'], and [17'] is the difference between the right-hand side and left-hand
side of the form. The weights are defined by the corresponding inverse covariance
matrices.
[0086] An exemplary estimation process for the floating ambiguities according to the present
invention employs form [31] in an iterative manner. We start at the initial epoch
k=0 with the weighting matrix Do set to the zero matrix, and an initial guess of floating
ambiguities
Δ1,0N0 equal to zero. The first term of form [31] evaluates to zero for this initial epoch.
We then generate a set of values for
δXk, Δ
1,0τ
k, δ1,0Ik,
Δ1,0Nk at a first epoch
k=1 which moves the value of
FΣ towards zero. This generates an initial estimate
Δ1,0N1 for the floating ambiguities and the rover's position (by way of
δX1). A weighting matrix
D1 for the ambiguities is then generated, and a new set of values is generated for
δXk, Δ
1,0τ
k δ1,0Ik,
Δ1,0Nk the next epoch
k=2 which moves value of
FΣ (k=2) towards zero. As a result, subsequent estimates
Δ1,0N2 and
δX2 are generated. This iteration process continues, with
Δ1,0Nk and
δXk generally improving in accuracy as the iterations progress.
[0087] Generating the values of
δXk, Δ
1,0τ
k,
δ1,0Ik,
Δ1,0Nk to minimize form [31] can be done in the following manner. Form [31] is constructed
in a manner whereby each term is generally of the form: (
M·Y -b)T ·W· (M·Y-b), where
Y is a vector of unknowns (
e.g., some or all of
δXk, Δ
1,0τ
k,
δ1,0Ik,
Δ1,0Nk),
M is a matrix of constants which multiply the unknowns (
e.g., Ak, c),
b is a vector of known values (
e.g.,
), and W is a weighting matrix (
e.g.,
Dk,
). The term
(M·Y -b)T ·W· (M·Y-b) can be reduced in value towards zero by generating a vector
Y which satisfies the relationship
(MT·W·M)·Y =
MT·W·b, which we can simplify as
H·Y =
B. If
H is not singular, we may apply an LU-decomposition method on
H to find
Y. The contributions of the six terms of form [31] may be synthesized according to the
following form:
where
H00 is a 3-by-3 matrix with the following form:
where
H10 is a 1-by-3 row vector with the following form:
where
H20 is an
N-by-3 matrix with the following form:
where
H30 is a 2
N-by-3 matrix with the following form:
where
h11 is a 1-by-1 matrix with the following form:
where
h21 is an
N-by-3 matrix with the following form:
where
h31 is a 2
N-by-1 column vector with the following form:
where
H22 is an
N-by-N matrix with the following form:
where
H32 is a 2
N-by-N matrix with the following form:
where
H33 is a 2
N-by-2
N matrix with the following form:
where
B0,k is a 3-by-1 column vector with the forms:
where
B1,k is a single value with the forms:
where
B2,k is an
N-by-1 column vector with the forms:
and where
B3,k is a 2
N-by-1 column vector with the form:
The matrix
Hk of form [32] is symmetric, and can be decomposed by a Cholesky factorization process
into the form:
Then, the unknown vector
can be generated by a conventional forward and backward substitution processes by
generating an intermediate matrix
Ỹ from the form
Lk Ỹ =
Bk, and then generating matrix
Yk from
LkT Yk = Ỹ, where
This generates an updated set of floating ambiguities and updated rover position.
Next, matrix
Dk for the next iteration is generated as follows:
Dk =
L33,
k L33Tk. The next iteration is then started by generating a new matrix
H based on another epoch of data, and thereafter reiterating the above steps. While
the epochs of data are generally processed in sequential time order, that is not a
requirement of the present invention. In a post-processing situation, the epochs may
be processed in any order. It can be shown that the matrix
Dk =
L33,k L33Tk is mathematically equivalent to the following form:
Matrix
Dk is the matrix of the second partial derivatives of the cost function
FΣ (
δXk, Δ
1,0τ
k,
δ1,0Ik,
Δ1,0Nk) partially minimized with respect to the variables
δXk, Δ
1,0τ
k,
δ1,0Ik :
[0088] The above process of generating the values of
δXk , Δ
1,0τ
k δ1,0Ik, and
Δ1,0Nk which minimizes the cost function
FΣ (
δXk, Δ
1,0τ
k,
δ1,0Ik,
Δ1,0Nk) generates an estimate for the position of Rover as
X0 = (
X0 +
δXk), which has an accuracy which is acceptable for many applications. Higher accuracy
generally results if we generate a set of fixed-integer ambiguities
Δ1,0N̂k from the floating ambiguities
Δ1,0Nk, and generate an estimate of the rover position from the fixed-integer ambiguities.
Examples of this are described in the next section.
[0089] The means for performing then above steps in rover 100 are provided by main processor
110 under the direction of instruction sets stored in memory 112, with the various
computed data being stored in data memory 114.
Fixed-Integer Ambiguity Resolution
[0090] Having at hand the estimation of the floating ambiguities
Δ1,0Nk, we describe an inventive method of generating the fixed-integer ambiguities
which may be used alone or in combination with the processes described above. The
components of the vector
Δ1,0N̂L1,k have the same fractional part Δ
ψL1, and the components of vector
Δ1,0N̂L2,k have the same fractional part Δ
ψL2. Having at hand the matrix
Dk and the vector
Δ1,0Nk, the embodiment forms the following cost function form:
The embodiment generates the values of
Δ1,0N̂k which minimize the value of
F(
Δ1,0N̂k) subject to the conditions:
and
where Z
nk denotes the domain of integer valued vectors (vectors having only integer components).
To generate the values of
Δ1,0N̂k, two reference satellites
ŝL1 and
ŝL2 are selected for the first and the second frequency bands. A between-satellite double
difference matrix
Σ is then generated, and will be applied to matrix
Δ1,0Nk. Matrix
E comprises a 2
N-by-2
N identity matrix, but with the columns associated with satellites
ŝL1 and
ŝL2 being modified, as shown below:
The columns are modified by substituting a value of -1 for each column element that
would normally be zero in the identity matrix. The positions of columns of matrix
E which are associated with satellites
ŝ1 and
ŝ2 correspond to the row positions of these satellites in the vector
Δ1,0Nk. When matrix
Σ is multiplied onto vector
Δ1,0Nk, the floating ambiguities corresponding to satellites
ŝL1 and
ŝL2 remain unchanged, but the floating ambiguity associated with
ŝL1 is subtracted from the other floating ambiguities in the L1-band, and the floating
ambiguity associated with
ŝL2 is subtracted from the other floating ambiguities in the L2-band. Next, a permutation
matrix
Π is generated, and is applied to matrix
Σ to generated a matrix product
Π·Σ. Permutation matrix is constructed to move the
ŝ1 and
ŝ2 columns of matrix E to the first and second column positions of the matrix product
Π·Σ. The construction of permutation matrices is well known to the field of mathematics.
A permutation matrix satisfies the following relationships:
ΠT·Π =
Π·ΠT = I. Next, a change of variables for the cost function F is undertaken as follows:
and the cost function can be formed as:
The first two components of
M̂k are real valued components (floating point numbers) and the remaining 2
N-2 components are integers. Let us divide the matrix
Gk into appropriate blocks in accordance with division of the vectors
and
where
G11,k is a 2-by-2 matrix,
G21,k is a 2-by-(2
N-2) matrix, and where
G22,k is a (2
N-2)-by-(2
N-2) matrix. This partitioning enables us to use a two step process of minimizing
by first generating values of
M̂1,k that reduce the value of
F(
M̂k), and thereafter generating values of
M̂2,k that further reduce the value of
F(
M̂k). We notate this two step process as:
The first step (inner minimization) of generating
M̂1,k to reduce
F(
M̂k) is performed in the space of floating point numbers (real valued space), and generates
M̂1,k in a form equivalent to:
the second step (outer minimization) of generating
M̂2,k is performed by substituting the form [41] of
M̂1,k into form [40] to generate the following modified version thereof:
Then, a search of an integer subspace for values of
M̂2,k is performed to find a set of integers which provides the smallest value of the modified
form [42]. The integer subspace can be relatively small, and centered about the floating
point values of
M2,k. After the integer search of form [42] is performed, the result
M̂2,k is substituted into form [41] to generate a revised vector
M̂1,k. Then, the change of variables operation (form [38]) is reversed as follows to generate
the fixed-integer ambiguities
Δ1,0N̂k as:
Δ1,0N̂k may then be separated into its components
and
[0091] As an option, an ambiguity resolution validation procedure may be performed to check
for consistency in the ambiguity resolution. This procedure is conventional, and the
reader is referred to prior art literature for a description thereof.
[0092] Having resolved the fixed-integer ambiguities, we can new generate a further refined
estimate of the other solvable unknowns:
δXk, Δ
1,0τ
k,
δ1,0Ik. A third cost function is formed as follows:
where the five terms of the form are the same as the second through sixth terms of
form [31], except that floating ambiguities have been replaced by the fixed-integer
ambiguities. The same estimation procedures used on form [31] may be applied above
to form [44], except that only one iteration is needed, and matrix
D is not generated.
[0093] The means for performing then above steps in rover 110 are provided by main processor
110 under the direction of instruction sets stored in memory 112, with the various
computed data being stored in data memory 114.
[0094] If lower accuracy can be tolerated, we may apply the process on form [44] using the
floating point ambiguities rather than the fixed-integer ambiguities. In this case,
the above fixed-integer ambiguity resolution process may be omitted.
Between Base Station Processing, Part II
[0095] In the above embodiments, the data of forms [6] and/or [7] were provided to the rover
station. However, because several of the rover-to-base station processes described
above are more efficient than those in the prior art, it is possible for the rover
itself to undertake the task of generating some or all of forms [6] and [7] at the
rover location, in real-time, from phase and pseudo-range measurements conveyed from
the base stations to the rover. This information may be conveyed by radio-signals
from the base stations to the rover, as described above. One may also implement a
system whereby the base stations convey their information to a relay station by cable
(such as the internet), with the relay station positioned within a few kilometers
of the rover station. The relay station then relays the base station data to the rover
by radio-signals.
[0096] In these embodiments, the rover receives the following data from each base station
"r" (r = 1, 2, 3) for several epochs
and
The locations of the base stations are also obtained:
X1,
X2, and
X3. As indicated previously, the locations of the satellites are highly predictable
and can readily be determined by the rover with its clock and correction data from
the almanac data transmitted by the satellites. From this, the rover generates the
computed ranges
from each rover "r" to each satellite "s" of a group of satellites being tracked.
As before, the troposphere delay terms are estimated from the Goad-Goodman model.
[0097] With this information, the residuals (difference quantities)
and
of forms [4A-4D] are generated for each baseline (q, r), where (q, r) has the following
pairings (B2, B1), (B3, B1), and (B2, B3). For each baseline, the solvable unknowns
in forms [5A-5D] are Δ
q,rτ
k,
Δq,rIk, and
Δq,rNk, Values are estimated from the residuals in a manner similar to that described about
for the primary baseline between the Rover and first base station. As an example,
a cost function F(*) may be formed as follows:
wherein the covariance matrices
σq,r are generated in a similar manner as the covariance matrices for the primary baseline.
[0098] The floating ambiguities may be estimated in an iterative manner as described above.
We start at the initial epoch
k=0 with the weighting matrix Do set to the zero matrix, and an initial guess of floating
ambiguities
Δq,rN0 equal to zero. The first term of form [31] evaluates to zero for this initial epoch.
We then generate a set of values for Δ
q,rτ
k,
Δq,rIk,
Δq,rNk, at a first epoch
k=1 which moves the value of F towards zero. This generates an initial estimate
Δq,rN1 for the floating ambiguities. A weighting matrix
D1 for the ambiguities is then generated, and a new set of values is generated for Δ
q,rτ
k,
Δq,rIk,
Δq,rNk at the next epoch
k=2 which moves value of
F (k=2) towards zero. As a result, subsequent estimates
Δq,rN2, is generated. This iteration process continues, with
Δq,rNk generally improving in accuracy as the iterations progress. The corresponding
H·Y =
B form for this process (similar to form [32]) is as follows:
where
h11 is a 1-by-1 matrix with the following form:
where
h21 is an
N-by-3 matrix with the following form:
where
h31 is a 2
N-by-1 column vector with the following form:
where
H22 is an
N-by-
N matrix with the following form:
where
H32 is a 2
N-by-
N matrix with the following form:
where
H33 is a 2
N-by-2
N matrix with the following form:
where
B1,k is a single value with the forms:
where
B2,k is an
N-by-1 column vector with the forms:
and where
B3,k is a 2
N-by-1 column vector with the form:
The matrix
Hk of form [46] is symmetric, and can be decomposed by a Cholesky factorization process
into the form:
Then, the unknown vector
can be generated by a conventional forward and backward substitution processes by
generating an intermediate matrix
Ỹ from the form
Lk Ỹ =
Bk, and then generating matrix
Yk from
LkTYk =
Ỹ, where
This generates an updated set of floating ambiguities and updated rover position.
Next, matrix
Dk for the next iteration is generated as follows:
Dk =
L33,k L33Tk. The next iteration is then started by generating a new matrix
H based on another epoch of data, and thereafter reiterating the above steps. While
the epochs of data are generally processed in sequential time order, that is not a
requirement of the present invention. In a post-processing situation, the epochs may
be processed in any order. It can be shown that the matrix
Dk =
L33,k L33Tk is mathematically equivalent to the following form:
Matrix
Dk is the matrix of the second partial derivatives of the cost function
F(Δ
q,rτ
k,
Δq,rIk,
Δq,rNk,) partially minimized with respect to the variables Δ
q,rτ
k,
Δq,rIk:
where
The corresponding fixed-integer ambiguities
Δq,rN̂k, may be generated from the floating ambiguities
Δq,rNk, by the same process described above with reference to forms [37] - [43] that is
used to generate the fixed-integer ambiguities associated with the primary base line
between the rover (R) and first base station (B1).
[0099] Having resolved the fixed-integer ambiguities, we can new generate a further refined
estimate of the other solvable unknowns: Δ
q,rτ
k, and
Δq,rIk. A third cost function is formed as follows:
where the five terms of the form are the same as the second through sixth terms of
form [45], except that floating ambiguities have been replaced by the fixed-integer
ambiguities. The same estimation procedures used on form [45] may be applied above
to form [51], except that only one iteration is needed, and matrix
D is not generated or used. As a result, estimates for and
Δq,rIk are generated. However, we prefer to perform some consistency checks on these estimates
before providing to the process that operates on the primary baseline between the
rover and the first base station. Thus, we will denote these estimates with hat symbols
as follows: Δ
q,rτ̂
k, and
Δq,rÎk, After the estimates associated with the three base line (q,r) = (B2, B1), (B3, B1),
(B3, B1) have been generated for the k-th epoch, we have the following data:
Δ2,1τ̂k, Δ2,1Îk, Δ2,1N̂k,
Δ3,1τ̂k, Δ3,1Îk, Δ3,1N̂k, and
Δ3,2τ̂k, Δ3,2Îk, Δ3,2N̂k.
We first perform an ambiguity resolution closure check. In this check, the following
relationships should hold:
which is equivalent to:
If the above relationships are not satisfied, the ambiguities have been resolved
incorrectly for at least one base line, and the estimations of fixed ambiguity should
be neglected. To address an incorrect resolution, new data may be taken, various subsets
of data may be processes to generate sets of ambiguities which satisfy the above relationships.
After all three between base receivers ambiguity have been resolved and the above
relationships are satisfied, the ambiguity vectors
Δ2,1N̂k,
Δ3,1N̂k, and
Δ3,2N̂k, are considered to be correctly fixed.
[0100] The time delays are similarly checked and corrected by taking new data or searching
existing data sets. In this check, the following relationships should hold:
which is equivalent to: Δ
2,1τ̂
k + Δ
3,2τ̂
k- Δ
3,1τ̂
k = 0, to within a tolerance value of ±∈
1, [53B]
where ∈
1 is a tolerance level which is close to zero. In general, ∈
1 depends upon the distances between baselines and the desired degree of accuracy for
the system. If the above relationships hold, then we validate these delays (
i.e., Δ
2,1τ
k = Δ
2,1τ̂
k, Δ
3,1τ
k = Δ
3,1τ̂
k, and Δ
3,2τ
k = Δ
3,2τ̂
k).
[0101] Next, we perform a consistency check on the ionosphere delays. In the following discussion,
we the subscripts on the ionosphere delay differentials have sometimes been exchanged,
but this is of no substantive consequence since
Δ1,2Îk =
Δ2,1Îk,
Δ2,3Îk =
-Δ3,2Îk and
Δ1,3Îk =
-Δ3,1Îk. The between base receivers ionosphere estimations should satisfy the relationship
However, measurements noise typically prevents these relationships from being satisfied
to an acceptable tolerance level ±∈
2. To better satisfy [54], the following quadratic function is minimized to obtain
new estimations
Δ1,2Ĩk,
Δ2,3Ĩk Δ3,1Ĩk:
provided the condition of:
is satisfied. The ionosphere estimations covariance matrices
C1,2,C2,3,C3,1 are estimated in the previous process by conventional methods. The inventors have
found that the following form minimizes form [55] subject to condition [56]:
Before applying form [57], the vectors
Δ1,2Îk,
Δ2,3Îk,
Δ3,1Îk are preferably smoothed using Kalman filtering scheme with a dynamic model based
the above described the Gauss-Markov time model (forms [GM1] and [GM2] above).
[0102] The results of these process may be provided to the process which generates the ionosphere
delay differentials for the baselines associated with the rover stations, specifically
the differentials generated according to forms [26], [29], and [30]. For form [26],
which generates
Δ1,0Ĩk, the results are provided as follows:
Δ1,2Ik =
Δ1,2Ĩk and
Δ1,3Îk =
Δ1,3Ĩk For generating the ionosphere delay differentials according to form [29] we set
Δ2,1Ik =
-Δ1,2Ĩk. For generating the ionosphere delay differentials according to form [30] we set
Δ3,1Ik =
Δ3,1Ĩk.
[0103] Thus, to summarize a preferred embodiment of the present invention, at each epoch
"
k" the following occurs for the three baselines between the base stations:
- Update of the floating ambiguity estimates by way of forms [45]-[50],
- Generate fixed-integer ambiguities (with a process similar to that illustrated by
forms [37] - [43]);
- Generate estimates of Δq,rτk and Δq,rIk by way of form [51] with a process similar to that illustrated by forms [45]-[50]
- Check consistency of the ambiguities (Δ2,1 N̂k + Δ3,2N̂k + Δ1,2N̂k = 0) and time offsets Δ2,1τ̂k Δ3,2τ̂k Δ1,3τ̂k = 0);
- Generate adjusted estimates Δ1,2Ĩk,Δ2,3Ĩk,Δ3,1Ĩk of the ionosphere delay differentials;
- Provide these results to the process of estimating the rover's position using the
primary and secondary baselines.
[0104] The above base-station to base-station data can be generated by the rover, or by
an external source, such as relay station. In the case of rover 100, the means for
performing all of the above steps are provided by Between-Base Station processor 140
under the direction of instruction sets stored in an instruction memory, with the
various computed data being stored in a data memory. Moreover, while higher accuracy
is obtained by generating the fixed-integer ambiguities, lower accuracy embodiments
may just generate the floating ambiguities.
[0105] While it is preferable to interpolate the ionosphere delays using two baselines between
three base stations, it may be appreciated that some application may achieve acceptable
accuracy by only interpolating the ionosphere delays using one baseline between two
base stations. Such an example may be a road project where the road is relatively
straight, as shown in FIG. 4.
[0106] Each of the above methods of generating the base station data and estimating the
coordinates of the rover is preferably implemented by a data processing system, such
as a microcomputer, operating under the direction of a set of instructions stored
in computer-readable medium, such as ROM, RAM, magnetic tape, magnetic disk,
etc. All the methods may be implements on one data processor, or they may be divided among
two or data processors.
Computer Program Products
[0107] It may be appreciated that each of the above methods may comprise the form of a computer
program to be installed in a computer for controlling the computer to perform the
process for estimating the location of a rover station (R) with the use of at least
a first base station (B1) and a second base station (B2), with the process comprising
the various steps of the method.
[0108] In addition, each of the above methods of generating the base station data and estimating
the coordinates of the rover may be implemented by a respective computer program product
which directs a data processing system, such as a microcomputer, to perform the steps
of the methods. Each computer program product comprises a computer-readable memory,
such for example as ROM, RAM, magnetic tape, magnetic disk,
etc., and a plurality of sets of instructions embodied on the computer-readable medium,
each set directing the data processing system to execute a respective step of the
method being implemented. FIG. 7 shows an exemplary comprehensive listing of instructions
sets for implementing the above method. Each of the above methods is achieved by selecting
the corresponding groups of instruction sets (as apparent from the above discussions).
Instruction set #18 is common to all of the methods, and is modified to omit the data
which is not used by the particular method.
[0109] While the present invention has been particularly described with respect to the illustrated
embodiments, it will be appreciated that various alterations, modifications and adaptations
may be made based on the present disclosure, and are intended to be within the scope
of the present invention. While the invention has been described in connection with
what is presently considered to be the most practical and preferred embodiments, it
is to be understood that the present invention is not limited to the disclosed embodiments
but, on the contrary, is intended to be limited only by the scope of the appended
claims.
1. A method of estimating the location of a rover station (R) with the use of a first
base station (B1) and a second base station (B2), the method comprising:
(a) (202) receiving known locations of the first base station and the second base
station;
(b) (206) receiving measured satellite navigation data as received by the rover station,
the first base station, and the second base station;
(c) (208) obtaining a first time offset representative of a difference between a first
offset from true GPS time of the clock of the first base station and a second offset
from true GPS time of the clock of the second base station;
(d) (214) generating a first set of residuals of differential navigation equations
associated with a first baseline (R-B1) between the rover station and the first base
station, the residuals being related to the measured satellite navigation data received
by the rover station and the first base station, the locations of the satellites,
and the locations of the rover station and the first base station;
(e) (214) generating a second set of residuals of differential navigation equations
associated with a second baseline (R-B2) between the rover station and the second
base station, the residuals being related to the measured satellite navigation data
received by the rover station and the second base station, the locations of the satellites,
and the locations of the rover station and the second base station;
(f) substituting, within the second set of residuals, an unknown time offset associated
with the second baseline (R-B2) with a value composed of a sum of the first time offset
and a time offset associated with the first baseline (R-B1); and
(g) (218) generating, subsequent to the substitution step of (f), an estimate of the
rover station's location from the first set of residuals, the second set of residuals
and the first time offset.
2. The method of Claim 1 further comprising the steps of:
(h) (202) receiving the location of a third base station (B3);
(i) (206) receiving measured satellite navigation data as received by the third base
station; and
(j) (208) obtaining a second time offset representative of the difference between
the first offset from true GPS time of the clock of the first base station and a third
offset from true GPS time of the clock of the third base station;
(k) (214) generating a third set of residuals of differential navigation equations
associated with a third baseline (R-B3) between the rover station and the third base
station, the residuals being related to the satellite navigation data received by
the rover station and the third base station, the locations of the satellites, and
the locations of the rover station and the third base station;
(1) substituting, within the third set of residuals, an unknown time offset associated
with the third baseline (R-B3) with a value composed of a sum of the second time offset
and a time offset associated with the first baseline (R-B1); and
wherein step (g) generates, subsequent to the substitution step of (1), the estimate
of the rover station's location further from the third set of residuals and the second
time offset.
3. The method of Claim 1 wherein step (c) comprises the step of generating the first
time offset.
4. The method of Claim 2 wherein step (c) comprises the step of generating the first
time offset and wherein step (j) comprises the step of generating the second time
offset.
5. The method of Claim 4 further comprising the steps of generating a third time offset
representative of a difference between the second offset from true GPS time of the
clock of the second station and the third offset from true GPS time of the clock of
the third base station, and comparing the sum of the first time offset, the second
time offset and the third time offset around a loop of the base stations to the value
of zero.
6. The method of Claim 1 or claim 2 wherein the first and second sets of residuals are
based on pseudo-range data, and wherein said method further comprises the step of
generating a first set of carrier-phase-based residuals of differential navigation
equations for the first baseline (R-B1) between the rover station and the first base
station, the first set of carrier-phase-based residuals being related to at least
the measured satellite carrier-phase data received by the rover station and the first
base station, the locations of the satellites, and the locations of the rover station
and the first base station; and
wherein step (g) generates the estimate of the rover station's location further from
the first set of carrier-phase-based residuals.
7. The method of Claim 6 further comprising the steps of:
obtaining a first set of satellite carrier-phase cycle ambiguities associated with
the baseline between the first and second base stations;
generating a second set of carrier-phase-based residuals of differential navigation
equations associated with the second baseline (R-B2) between the rover station and
the second base station, the second set of carrier-phase-based residuals being related
to at least the measured satellite carrier-phase data received by the rover station
and the second base station, the locations of the satellites, and the locations of
the rover station and the second base station; and
wherein step (g) generates the estimate of the rover station's location further from
the second set of carrier-phase-based residuals and the first set of satellite-phase
cycle ambiguities.
8. The method of Claim 7 wherein claim 6 is dependent on claim 2, further comprising
the steps of:
obtaining a second set of satellite carrier-phase cycle ambiguities associated with
the baseline between the first and third base stations;
generating a third set of carrier-phase-based residuals of differential navigation
equations associated with the third baseline (R-B3) between the rover station and
the third base station, the third set of carrier-phase-based residuals being related
to at least the measured satellite carrier-phase data received by the rover station
and the third base station, the locations of the satellites, and the locations of
the rover station and the third base station; and
wherein step (g) generates the estimate of the rover station's location further from
the third set of carrier-phase-based residuals and the second set of satellite-phase
cycle ambiguities.
9. The method of Claim 6 further comprising the step of generating a first set of floating
ambiguities for the baseline between the rover station and first base station from
the first set of carrier-phase-based residuals and at least one of the sets of residuals
based on pseudo-range data; and
wherein step (g) generates the estimate of the rover station's location further from
the first set of floating ambiguities.
10. The method of Claim 6 further comprising the steps of:
generating a first set of floating ambiguities for the baseline between the rover
station and first base station from the first set of carrier-phase-based residuals
and at least one of the sets of residuals based on pseudo-range data; and
generating a first set of fixed-integer floating ambiguities for the baseline between
the rover station and first base station from the first set of floating ambiguities;
wherein step (g) generates the estimate of the rover station's location further from
the first set of fixed-integer floating ambiguities.
11. The method of Claim 7 further comprising the step of:
generating a first set of floating ambiguities for the baseline between the rover
station and first base station from the first set of carrier-phase-based residuals,
the second set of carrier-phase-based residuals, the first set of satellite carrier-phase
cycle ambiguities related to the baseline between the first and second base stations,
and at least one of the sets of residuals based on pseudo-range data;
wherein step (g) generates the estimate of the rover station's location further from
the first set of floating ambiguities.
12. The method of Claim 6 further comprising the steps of:
generating a first set of floating ambiguities for the baseline between the rover
station and first base station from the first set of carrier-phase-based residuals,
the second set of carrier-phase-based residuals, the first set of satellite carrier-phase
cycle ambiguities related to the baseline between the first and second base stations,
and at least one of the sets of residuals based on pseudo-range data;
generating a first set of fixed-integer floating ambiguities for the baseline between
the rover station and first base station from the first set of floating ambiguities;
wherein step (g) generates the estimate of the rover station's location further from
the first set of fixed-integer floating ambiguities.
13. The method of Claim 8 further comprising the step of:
generating a first set of floating ambiguities for the baseline between the rover
station and first base station from the first set of carrier-phase-based residuals,
the second set of carrier-phase-based residuals, the first set of satellite carrier-phase
cycle ambiguities related to the baseline between the first and second base stations,
the third set of carrier-phase-based residuals, the second set of satellite carrier-phase
cycle ambiguities related to the baseline between the first and second base stations,
and at least one of the sets of residuals based on pseudo-range data;
wherein step (g) generates the estimate of the rover station's location further from
the first set of floating ambiguities.
14. The method of Claim 8 further comprising the steps of:
generating a first set of floating ambiguities for the baseline between the rover
station and first base station from the first set of carrier-phase-based residuals,
the second set of carrier-phase-based residuals, the first set of satellite carrier-phase
cycle ambiguities related to the baseline between the first and second base stations,
the third set of carrier-phase-based residuals, the second set of satellite carrier-phase
cycle ambiguities related to the baseline between the first and second base stations,
and at least one of the sets of residuals based on pseudo-range data;
generating a first set of fixed-integer floating ambiguities for the baseline between
the rover station and first base station from the first set of floating ambiguities;
wherein step (g) generates the estimate of the rover station's location further from
the first set of fixed-integer floating ambiguities.
15. The method according to any of the above claims further comprising the steps of:
obtaining a first set of first ionosphere delay differentials associated with the
satellite signals received along the baseline formed by the first and second base
stations, and
generating corrections to one or more of the residuals, the corrections being related
to the first set of first ionosphere delay differentials, the locations of the first
and second base stations, and an estimated location of the rover station; and
modifying said one or more of the residuals with said corrections.
16. The method according to claim 8 further comprising the steps of:
obtaining a first set of first ionosphere delay differentials associated with the
satellite signals received along the baseline formed by the first and second base
stations,
obtaining a second set of second ionosphere delay differentials associated with the
satellite signals received along the baseline formed by the first and third base stations,
and
generating corrections to one or more of the residuals, the corrections being related
to the first set of first ionosphere delay differentials, the second set of second
ionosphere delay differentials, the locations of the base stations, and an estimated
location of the rover station; and
modifying said one or more of the residuals with said corrections.
17. The method of Claim 16 wherein the correction to the residuals associated with satellite
"s" in one or both of the second set of residuals and the second set of carrier-phase-based
residuals is related to the quantity
where
is the first ionosphere delay differential associated with satellite "s", and
is an estimated ionosphere delay differential associated with satellite "s" along
the baseline between the rover station and first base station.
18. The method of Claim 16 wherein the correction to the residuals associated with satellite
"s" in one or both of the third set of residuals and the third set of carrier-phase-based
residuals is related to the quantity
where
is the second ionosphere delay differential associated with satellite "s", and
is an estimated ionosphere delay differential associated with satellite "s" along
the baseline between the rover station and first base station.
19. The method of Claim 16 wherein the ionosphere delay differential from the first set
and associated with satellite "s" may be denoted as
wherein the ionosphere delay differential from the second set and associated with
satellite "s" may be denoted as
wherein the locations of the first, second, and third base stations may be represented
by the vectors
X1, X2, and
X3 , and wherein the estimated location of the rover station may be represented as
X0,k,
wherein the corrections to one or more of the residuals associated with satellite
"s" are related to a quantity
where
wherein
α and
β are constants that satisfy the relationships:
where notation
{ *
}n denotes the component of the bracketed quantity along the north direction, where
notation
{ *
}e denotes the component of the bracketed quantity along the east direction.
20. The method of Claim 19 wherein the correction to the residuals associated with satellite
"s" in one or both of the second set of residuals and the second set of carrier-phase-based
residuals is related to the quantity
where
is the first ionosphere delay differential associated with satellite "s".
21. The method of Claim 19 wherein the correction to the residual associated with satellite
"s" in one or both of the third set of residuals and the third set of carrier-phase-based
residuals is related to the quantity
where
is the second ionosphere delay differential associated with satellite "s".
22. The method according to Claim 16 further comprising the steps of:
modifying one or more of the above residuals to be dependent upon second order effects
in the ionosphere delay corrections applied to the baselines associated with the rover
station, and
generating an estimate of the second order effects, and
wherein step (g) generates the estimate of the rover station's location further from
the estimated second order effects.
23. The method according to Claim 16 wherein the method generates the first set of first
ionosphere delay differentials and the second set of second ionosphere delay differentials
from at least the navigation data that it receives from the base stations.
24. The method according to Claim 16 further comprising the steps of:
generating an initial estimate of the first set of first ionosphere delay differentials
associated with the satellite signals received along the baseline formed by the first
and second base stations;
generating an initial estimate of second set of second ionosphere delay differentials
associated with the satellite signals received along the baseline formed by the first
and third base stations;
generating an initial estimate of a third set of third ionosphere delay differentials
associated with the satellite signals received along the baseline formed by the second
and third base stations; and
generating final estimates of the ionosphere delay differentials such that the sum
of the final estimates of the first, second, and third ionosphere delay differentials
for at least one satellite "s" around a loop of the base stations is substantially
zero.
25. The method of Claim 7 wherein the step of obtaining the first set of satellite carrier-phase
cycle ambiguities comprises the step of generating the first set of satellite carrier-phase
cycle ambiguities from at least the locations of the base stations, and measured satellite
navigation data as received by the base stations.
26. The method of Claim 8 wherein the steps of obtaining the first and second sets of
satellite carrier-phase cycle ambiguities comprises the step of generating the first
set of satellite carrier-phase cycle ambiguities from at least the locations of the
first and second base stations and measured satellite navigation data as received
by the first and second base stations, and the step of generating the second set of
satellite carrier-phase cycle ambiguities from at least the locations of the first
and third base stations and measured satellite navigation data as received by the
first and third base stations.
27. The method of Claim 26 further comprising the steps of generating a third set of satellite
carrier-phase cycle ambiguities associated with the baseline between the second and
third base stations, and comparing the sum of the three sets of satellite carrier-phase
ambiguities around a loop of the base stations to the value of zero.
28. A computer program which, when run on a computer processor, causes the computer processor
to carry out the method of any preceding claim.
29. An apparatus for estimating the location of a rover station (R) with the use of a
first base station (B1) and a second base station (B2), the apparatus comprising:
(a) means for receiving the locations of the first base station and the second base
station;
(b) means for receiving measured satellite navigation data as received by the rover
station, the first base station, and the second base station;
(c) means for obtaining a first time offset representative of a difference between
a first offset from true GPS time of the clock of the first base station and a second
offset from true GPS time of the clock of the second base station;
(d) means for generating a first set of residuals of differential navigation equations
associated with a first baseline (R-B1) between the rover station and the first base
station, the residuals being related to the measured satellite navigation data received
by the rover station and the first base station, the locations of the satellites,
and the locations of the rover station and the first base station;
(e) means for generating a second set of residuals of differential navigation equations
associated with a second baseline (R-B2) between the rover station and the second
base station, the residuals being related to the measured satellite navigation data
received by the rover station and the second base station, the locations of the satellites,
and the locations of the rover station and the second base station; and
(f) means for substituting, within the second set of residuals, an unknown time offset
associated with the second baseline (R-B2) with a value composed of a sum of the first
time offset and a time offset associated with the first baseline (R-B1); and
(g) means for generating , subsequent to the substitution of step (f), an estimate
of the rover station's location from the first set of residuals, the second set of
residuals and the first time offset.
30. The apparatus of Claim 29 further comprising:
(h) means for receiving the location of a third base station;
(i) means for receiving measured satellite navigation data as received by the third
base station;
(j) means for obtaining a second time offset representative of the difference between
the first offset from true GPS time of the clock of the first base station and a third
offset from true GPS time of the clock of the third base station;
(k) means for generating a third set of residuals of differential navigation equations
associated with a third baseline (R-B3) between the rover station and the third base
station, the residuals being related to the satellite navigation data received by
the rover station and the third base station, the locations of the satellites, and
the locations of the rover station and the third base station;
(1) means for substituting, within the third set of residuals, an unknown time offset
associated with the third baseline (R-B3) with a value composed of a sum of the second
time offset and a time associated with the first baseline (R-B1); and
wherein the means (g) for generating, subsequent to the substitution step of (1),
the estimate of the rover station's location generates the estimate further from the
third set of residuals and the second time offset.
31. The apparatus of Claim 29 wherein the means (c) for obtaining the first time offset
comprises means for generating the first time offset.
32. The apparatus of Claim 30 wherein the means (c) for obtaining the first time offset
comprises means for generating the first time offset and wherein the means (j) for
obtaining the second time offset comprises means for generating the second time offset.
33. The apparatus of Claim 32 further comprising means for generating a third time offset
representative of the time difference between the second offset from true GPS time
of the clock of the second base station and the third offset from true GPS time of
the clock of the third base station, and means for comparing the sum of the first
time offset, the second time offset, and the third time offset around a loop of the
base stations to the value of zero.
34. The apparatus of Claim 29 or claim 30 wherein the first and second sets of residuals
are based on pseudo-range data, and wherein the apparatus further comprises means
for generating a first set of carrier-phase-based residuals of differential navigation
equations for the first baseline (R-B1) between the rover station and the first base
station, the first set of carrier-phase-based residuals being related to at least
the measured satellite carrier-phase data received by the rover station and the first
base station, the locations of the satellites, and the locations of the rover station
and the first base station; and
wherein the means (g) for generating the estimate of the rover station's location
generates the estimate further from the first set of carrier-phase-based residuals.
35. The apparatus of Claim 34 further comprising:
means for obtaining a first set of satellite carrier-phase cycle ambiguities associated
with the baseline between the first and second base stations;
means for generating a second set of carrier-phase-based residuals of differential
navigation equations associated with the second baseline (R-B2) between the rover
station and the second base station, the second set of carrier-phase-based residuals
being related to at least the measured satellite carrier-phase data received by the
rover station and the second base station, the locations of the satellites, and the
locations of the rover station and the second base station; and
wherein the means (g) for generating the estimate of the rover station's location
generates the estimate further from the second set of carrier-phase-based residuals
and the first set of satellite-phase cycle ambiguities.
36. The apparatus of Claim 35 wherein claim 34 is dependent on claim 30 further comprising:
means for obtaining a second set of satellite carrier-phase cycle ambiguities associated
with the baseline between the first and third base stations;
means for generating a third set of carrier-phase-based residuals of differential
navigation equations associated with the third baseline (R-B3) between the rover station
and the third base station, the third set of carrier-phase-based residuals being related
to at least the measured satellite carrier-phase data received by the rover station
and the third base station, the locations of the satellites, and the locations of
the rover station and the third base station; and
wherein the means (g) for generating the estimate of the rover station's location
generates the estimate further from the third set of carrier-phase-based residuals
and the second set of satellite-phase cycle ambiguities.
37. The apparatus of Claim 32 further comprising means for generating a first set of floating
ambiguities for the baseline between the rover station and first base station from
the first set of carrier-phase-based residuals and at least one of the sets of residuals
based on pseudo-range data; and
wherein the means (g) for generating the estimate of the rover station's location
generates the estimate further from the first set of floating ambiguities.
38. The apparatus of Claim 34 further comprising:
means for generating a first set of floating ambiguities for the baseline between
the rover station and first base station from the first set of carrier-phase-based
residuals and at least one of the sets of residuals based on pseudo-range data; and
means for generating a first set of fixed-integer floating ambiguities for the baseline
between the rover station and first base station from the first set of floating ambiguities;
wherein the means (g) for generating the estimate of the rover station's location
generates the estimate further from the first set of fixed-integer floating ambiguities.
39. The apparatus of Claim 35 further comprising:
means for generating a first set of floating ambiguities for the baseline between
the rover station and first base station from the first set of carrier-phase-based
residuals, the second set of carrier-phase-based residuals, the first set of satellite
carrier-phase cycle ambiguities related to the baseline between the first and second
base stations, and at least one of the sets of residuals based on pseudo-range data;
wherein the means (g) for generating the estimate of the rover station's location
generates the estimate further from the first set of floating ambiguities.
40. The apparatus of Claim 35 further comprising:
means for generating a first set of floating ambiguities for the baseline between
the rover station and first base station from the first set of carrier-phase-based
residuals, the second set of carrier-phase-based residuals, the first set of satellite
carrier-phase cycle ambiguities related to the baseline between the first and second
base stations, and at least one of the sets of residuals based on pseudo-range data;
and
means for generating a first set of fixed-integer floating ambiguities for the baseline
between the rover station and first base station from the first set of floating ambiguities;
wherein the means (g) for generating the estimate of the rover station's location
generates the estimate further from the first set of fixed-integer floating ambiguities.
41. The apparatus of Claim 36 further comprising:
means for generating a first set of floating ambiguities for the baseline between
the rover station and first base station from the first set of carrier-phase-based
residuals, the second set of carrier-phase-based residuals, the first set of satellite
carrier-phase cycle ambiguities related to the baseline between the first and second
base stations, the third set of carrier-phase-based residuals, the second set of satellite
carrier-phase cycle ambiguities related to the baseline between the first and second
base stations, and at least one of the sets of residuals based on pseudo-range data;
wherein the means (g) for generating the estimate of the rover station's location
generates the estimate further from the first set of floating ambiguities.
42. The apparatus of Claim 36 further comprising:
means for generating a first set of floating ambiguities for the baseline between
the rover station and first base station from the first set of carrier-phase-based
residuals, the second set of carrier-phase-based residuals, the first set of satellite
carrier-phase cycle ambiguities related to the baseline between the first and second
base stations, the third set of carrier-phase-based residuals, the second set of satellite
carrier-phase cycle ambiguities related to the baseline between the first and second
base stations, and at least one of the sets of residuals based on pseudo-range data;
and
means for generating a first set of fixed-integer floating ambiguities for the baseline
between the rover station and first base station from the first set of floating ambiguities;
wherein the means (g) for generating the estimate of the rover station's location
generates the estimate further from the first set of fixed-integer floating ambiguities.
43. The apparatus according to any of the above claims 29 - 42 further comprising:
means for obtaining a first set of first ionosphere delay differentials associated
with the satellite signals received along the baseline formed by the first and second
base stations, and
means for generating corrections to one or more of the residuals, the corrections
being related to the first set of first ionosphere delay differentials, the locations
of the first and second base stations, and an estimated location of the rover station;
and
means for modifying said one or more of the residuals with said corrections.
44. The apparatus according to claim 36 further comprising:
means for obtaining a first set of first ionosphere delay differentials associated
with the satellite signals received along the baseline formed by the first and second
base stations,
means for obtaining a second set of second ionosphere delay differentials associated
with the satellite signals received along the baseline formed by the first and third
base stations, and
means for generating corrections to one or more of the residuals, the corrections
being related to the first set of first ionosphere delay differentials, the second
set of second ionosphere delay differentials, the locations of the base stations,
and an estimated location of the rover station; and
means for modifying said one or more of the residuals with said corrections.
45. The apparatus of Claim 44 wherein the correction to the residuals associated with
satellite "s" in one or both of the second set of residuals and the second set of
carrier-phase-based residuals is related to the quantity
where
is the first ionosphere delay differential associated with satellite "s", and
is an estimated ionosphere delay differential associated with satellite "s" along
the baseline between the rover station and first base station.
46. The apparatus of Claim 44 wherein the correction to the residuals associated with
satellite "s" in one or both of the third set of residuals and the third set of carrier-phase-based
residuals is related to the quantity
where
is the second ionosphere delay differential associated with satellite "s", and
is an estimated ionosphere delay differential associated with satellite "s" along
the baseline between the rover station and first base station.
47. The apparatus of Claim 44 wherein the ionosphere delay differential from the first
set and associated with satellite "s" may be denoted as
wherein the ionosphere delay differential from the second set and associated with
satellite "s" may be denoted as
wherein the locations of the first, second, and third base stations may be represented
by the vectors
X1, X2, and
X3, and wherein the estimated location of the rover station may be represented as
X0,k,
wherein the corrections to one or more of the residuals associated with satellite
"s" are related to a quantity
where
wherein
α and
β are constants that satisfy the relationships:
where notation
{ * }n denotes the component of the bracketed quantity along the north direction, where
notation
{*
}e denotes the component of the bracketed quantity along the east direction.
48. The apparatus of Claim 44 wherein the correction to the residuals associated with
satellite "s" in one or both of the second set of residuals and the second set of
carrier-phase-based residuals is related to the quantity
where
is the first ionosphere delay differential associated with satellite "s".
49. The apparatus of Claim 44 wherein the correction to the residual associated with satellite
"s" in one or both of the third set of residuals and the third set of carrier-phase-based
residuals is related to the quantity
where
is the second ionosphere delay differential associated with satellite "s".
50. The apparatus according to Claim 43 further comprising:
means for modifying one or more of the above residuals to be dependent upon second
order effects in the ionosphere delay corrections applied to the baselines associated
with the rover station, and
means for generating an estimate of the second order effects, and
wherein the means (i) for generating the estimate of the rover station's location
generates the estimate further from the estimated second order effects.
51. The apparatus according to Claim 43 wherein the apparatus generates the first set
of first ionosphere delay differentials and the second set of second ionosphere delay
differentials from at least the navigation data that it receives from the base stations.
52. The apparatus according to Claim 43 further comprising:
means for generating an initial estimate of the first set of first ionosphere delay
differentials associated with the satellite signals received along the baseline formed
by the first and second base stations;
means for generating an initial estimate of second set of second ionosphere delay
differentials associated with the satellite signals received along the baseline formed
by the first and third base stations;
means for generating an initial estimate of a third set of third ionosphere delay
differentials associated with the satellite signals received along the baseline formed
by the second and third base stations; and
means for generating final estimates of the ionosphere delay differentials such that
the sum of the final estimates of the first, second, and third ionosphere delay differentials
for at least one satellite "s" around a loop of the base stations is substantially
zero.
53. The apparatus of Claim 35 wherein the means for obtaining the first set of satellite
carrier-phase cycle ambiguities comprises means for generating the first set of satellite
carrier-phase cycle ambiguities from at least the locations of the base stations,
and measured satellite navigation data as received by the base stations.
54. The apparatus of Claim 36 wherein the means for obtaining the first and second sets
of satellite carrier-phase cycle ambiguities comprises means for generating the first
set of satellite carrier-phase cycle ambiguities from at least the locations of the
first and second base stations and measured satellite navigation data as received
by the first and second base stations, and means for generating the second set of
satellite carrier-phase cycle ambiguities from at least the locations of the first
and third base stations and measured satellite navigation data as received by the
first and third base stations.
1. Verfahren zum Abschätzen des Standortes einer Erkundungsstation (R) unter Verwendung
einer ersten Basisstation (B1) und einer zweiten Basisstation (B2), wobei das Verfahren
umfasst:
(a) (202) Empfangen bekannter Standorte der ersten Basisstation und der zweiten Basisstation;
(b) (206) Empfangen gemessener Satellitennavigationsdaten, wie durch die Erkundungsstation,
die erste Basisstation und die zweite Basisstation empfangen;
(c) (208) Erhalten eines ersten Zeitabstands, repräsentativ für einen Unterschied
zwischen einem ersten Abstand von einer wahren GPS-Zeit der Uhr der ersten Basisstation
und einem zweiten Abstand von einer wahren GPS-Zeit von der Uhr der zweiten Basisstation;
(d) (214) Erzeugen eines ersten Satzes von Residuen von Differenzialnavigationsgleichungen,
welche einer ersten Basislinie (R-B1) zwischen der Erkundungsstation und der ersten
Basisstation zugeordnet sind, wobei die Residuen in Beziehung stehen mit den von der
Erkundungsstation und der ersten Basisstation empfangenen gemessenen Satellitennavigationsdaten,
den Standorten der Satelliten und den Standorten der Erkundungsstation und der ersten
Basisstation;
(e) (214) Erzeugen eines zweiten Satzes von Residuen von Differenzialnavigationsgleichungen,
welche einer zweiten Basislinie (R-B2) zwischen der Erkundungsstation und der zweiten
Basisstation zugeordnet sind, wobei die Residuen in Beziehung stehen mit den von der
Erkundungsstation und der zweiten Basisstation empfangenen gemessenen Satellitennavigationsdaten,
den Standorten der Satelliten und den Standorten der Erkundungsstation und der zweiten
Basisstation;
(f) Substituieren, innerhalb des zweiten Satzes von Residuen, eines unbekannten Zeitabstands,
welcher der zweiten Basislinie (R-B2) zugeordnet ist, mit einem Wert, welcher aus
einer Summe des ersten Zeitabstands und eines Zeitabstands, welcher der ersten Basislinie
(R-B1) zugeordnet ist, zusammengesetzt ist; und
(g) (218) Erzeugen, dem Substitutionsschritt von (f) nachfolgend, eine Abschätzung
des Standortes der Erkundungsstation aus dem ersten Satz von Residuen, dem zweiten
Satz von Residuen und dem ersten Zeitabstand.
2. Verfahren nach Anspruch 1 ferner umfassend die Schritte:
(h) (202) Empfangen des Standortes einer dritten Basisstation (B3);
(i) (206) Empfangen gemessener Satellitennavigationsdaten, wie durch die dritte Basisstation
empfangen; und
(j) (208) Erhalten eines zweiten Zeitabstands, repräsentativ für den Unterschied zwischen
dem ersten Abstand von einer wahren GPS-Zeit von der Uhr der ersten Basisstation und
einem dritten Abstand von einer wahren GPS-Zeit von der Uhr der dritten Basisstation;
(k) (214) Erzeugen eines dritten Satzes von Residuen von Differenzialnavigationsgleichungen,
welche einer dritten Basislinie (R-B3) zwischen der Erkundungsstation und der dritten
Basisstation zugeordnet sind, wobei die Residuen in Beziehung stehen mit den von der
Erkundungsstation und der dritten Basisstation empfangenen Satellitennavigationsdaten,
den Standorten der Satelliten und den Standorten der Erkundungsstation und der dritten
Basisstation;
(I) Substituieren, innerhalb des dritten Satzes von Residuen, eines unbekannten Zeitabstands,
welcher der dritten Basislinie (R-B3) zugeordnet ist, mit einem Wert, welcher aus
einer Summe des zweiten Zeitabstands und eines Zeitabstands, welcher der ersten Basislinie
(R-B1) zugeordnet ist, zusammengesetzt ist; und
wobei Schritt (g), dem Substitutionsschritt (I) nachfolgend, die Abschätzung des Standortes
der Erkundungsstation ferner aus dem dritten Satz von Residuen und dem zweiten Zeitabstand
erzeugt.
3. Verfahren nach Anspruch 1, wobei Schritt (c) den Schritt eines Erzeugens des ersten
Zeitabstands umfasst.
4. Verfahren nach Anspruch 2, wobei Schritt (c) den Schritt eines Erzeugens des ersten
Zeitabstands umfasst und wobei Schritt (j) den Schritt eines Erzeugens des zweiten
Zeitabstands umfasst.
5. Verfahren nach Anspruch 4, ferner umfassend die Schritte eines Erzeugens eines dritten
Zeitabstands, repräsentativ für einen Unterschied zwischen dem zweiten Abstand von
einer wahren GPS-Zeit von der Uhr der zweiten Station und des dritten Abstands von
einer wahren GPS-Zeit von der Uhr der dritten Basisstation und Vergleichen der Summe
des ersten Zeitabstands, des zweiten Zeitabstands und des dritten Zeitabstands ringsum
einer Schlaufe von den Basisstationen mit dem Wert von null.
6. Verfahren nach Anspruch 1 oder Anspruch 2, wobei der erste und zweite Satz von Residuen
auf Pseudoabstandsdaten basieren und wobei das Verfahren ferner den Schritt eines
Erzeugens eines ersten Satzes von trägerphasenbasierten Residuen von Differenzialnavigationsgleichungen
für die erste Basislinie (R-B1) zwischen der Erkundungsstation und der ersten Basisstation
umfasst, wobei der erste Satz von trägerphasenbasierten Residuen in Bezug steht zu
mindestens den gemessenen Satellitenträgerphasendaten, welche durch die Erkundungsstation
und die erste Basisstation empfangen werden, den Standorten der Satelliten, und den
Standorten der Erkundungsstation und der ersten Basisstation; und
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
dem ersten Satz von trägerphasenbasierten Residuen erzeugt.
7. Verfahren nach Anspruch 6, ferner umfassend die Schritte:
Erhalten eines ersten Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten, welche
der Basislinie zwischen der ersten und zweiten Basisstation zugeordnet sind;
Erzeugen eines zweiten Satzes von trägerphasenbasierten Residuen von Differenzialnavigationsgleichungen,
welche der zweiten Basislinie (R-B2) zwischen der Erkundungsstation und der zweiten
Basisstation zugeordnet sind, wobei der zweite Satz von trägerphasenbasierten Residuen
in Bezug steht mit mindestens den gemessenen Satellitenträgerphasendaten, welche durch
die Erkundungsstation und die zweite Basisstation empfangen werden, den Standorten
der Satelliten, und den Standorten der Erkundungsstation und der zweiten Basisstation;
und
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
dem zweiten Satz von trägerphasenbasierten Residuen und dem ersten Satz von Satellitenphasenzyklusmehrdeutigkeiten
erzeugt.
8. Verfahren nach Anspruch 7, wobei Anspruch 6 von Anspruch 2 abhängig ist, ferner umfassend
die Schritte:
Erhalten eines zweiten Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten, welcher
der Basislinie zwischen der ersten und dritten Basisstation zugeordnet sind;
Erzeugen eines dritten Satzes von trägerphasenbasierten Residuen von Differenzialnavigationsgleichungen,
welche der dritten Basislinie (R-B3) zwischen der Erkundungsstation und der dritten
Basisstation zugeordnet sind, wobei der dritte Satz von trägerphasenbasierten Residuen
in Beziehung steht mindestens mit den gemessenen Satellitenträgerphasendaten, welche
durch die Erkundungsstation und die dritte Basisstation empfangen werden, den Standorten
der Satelliten, und den Standorten der Erkundungsstation und der dritten Basisstation;
und
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
dem dritten Satz von trägerphasenbasierten Residuen und dem zweiten Satz von Satellitphasenzyklusmehrdeutigkeiten
erzeugt.
9. Verfahren nach Anspruch 6, ferner umfassend den Schritt eines Erzeugens eines ersten
Satzes von Fließkommamehrdeutigkeiten für die Basislinie zwischen der Erkundungsstation
und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten Residuen und
mindestens einem aus den Sätzen von Residuen, welche auf Pseudoabstandsdaten basieren;
und
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
dem ersten Satz von Fließkommamehrdeutigkeiten erzeugt.
10. Verfahren nach Anspruch 6, ferner umfassend die Schritte:
Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie zwischen
der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen und mindestens einem aus den Sätzen von Residuen, welche auf Pseudoabstandsdaten
basieren; und
Erzeugen eines ersten Satzes von Fest-Integer-Fließkommamehrdeutigkeiten für die Basislinie
zwischen der Erkundungsstation und ersten Basisstation aus dem ersten Satz von Fließkommamehrdeutigkeiten;
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
dem ersten Satz von Fest-Integer-Fließkommamehrdeutigkeiten erzeugt.
11. Verfahren nach Anspruch 7, ferner umfassend den Schritt:
Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie zwischen
der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von trägerphasenbasierten Residuen, dem ersten Satz von
Satellitenträgerphasenzyklusmehrdeutigkeiten, welche in Beziehung stehen zu der Basislinie
zwischen der ersten und zweiten Basisstation, und mindestens einem aus den Sätzen
von Residuen, welche auf Pseudoabstandsdaten basieren;
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
dem ersten Satz von Fließkommamehrdeutigkeiten erzeugt.
12. Verfahren nach Anspruch 6, ferner umfassend die Schritte:
Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie zwischen
der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von trägerphasenbasierten Residuen, dem ersten Satz von
Satellitenträgerphasenzyklusmehrdeutigkeiten, welche in Beziehung stehen zu der Basislinie
zwischen der ersten und zweiten Basisstation, und mindestens einem aus den Sätzen
von Residuen, welche auf Pseudoabstandsdaten basieren;
Erzeugen eines ersten Satzes von Fest-Integer-Fließkommamehrdeutigkeiten für die Basislinie
zwischen der Erkundungsstation und ersten Basisstation aus dem ersten Satz von Fließkommamehrdeutigkeiten;
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
dem ersten Satz von Fest-Integer-Fließkommamehrdeutigkeiten erzeugt.
13. Verfahren nach Anspruch 8, ferner umfassend den Schritt:
Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie zwischen
der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von trägerphasenbasierten Residuen, dem ersten Satz von
Satellitenträgerphasenzyklusmehrdeutigkeiten, welche in Beziehung stehen zu der Basislinie
zwischen der ersten und zweiten Basisstation, dem dritten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von Satellitenträgerphasenzyklusmehrdeutigkeiten, welche
mit der Basislinie zwischen der ersten und zweiten Basisstation in Beziehung stehen,
und mindestens einem aus den Sätzen von Residuen, welche auf Pseudoabstandsdaten basieren;
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
dem ersten Satz von Fließkommamehrdeutigkeiten erzeugt.
14. Verfahren nach Anspruch 8, ferner umfassend die Schritte:
Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie zwischen
der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von trägerphasenbasierten Residuen, dem ersten Satz von
Satellitenträgerphasenzyklusmehrdeutigkeiten, welche mit der Basislinie zwischen der
ersten und zweiten Basisstation in Beziehung stehen, dem dritten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von Satellitenträgerphasenzyklusmehrdeutigkeiten, welche
mit der Basislinie zwischen der ersten und zweiten Basisstation in Beziehung stehen,
und mindestens einem aus den Sätzen von Residuen, welche auf Pseudoabstandsdaten basieren;
Erzeugen eines ersten Satzes von Fest-Integer-Fließkommamehrdeutigkeiten für die Basislinie
zwischen der Erkundungsstation und ersten Basisstation aus dem ersten Satz von Fließkommamehrdeutigkeiten;
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
dem ersten Satz von Fest-Integer-Fließkommamehrdeutigkeiten erzeugt.
15. Verfahren nach einem der vorhergehenden Ansprüche, ferner umfassend die Schritte:
Erhalten eines ersten Satzes von ersten lonosphärenverzögerungsdifferentialen, welche
den entlang einer zwischen der ersten und zweiten Basisstation ausgebildeten Basislinie
empfangenen Satellitensignalen zugeordnet sind, und
Erzeugen von Korrekturen für ein oder mehrere aus den Residuen, wobei die Korrekturen
in Beziehung stehen mit dem ersten Satz von ersten lonosphärenverzögerungsdifferentialen,
den Standorten der ersten und zweiten Basisstation und einem abgeschätzten Standort
der Erkundungsstation; und
Modifizieren des einen oder der mehreren aus den Residuen mit den Korrekturen.
16. Verfahren nach Anspruch 8, ferner umfassend die Schritte:
Erhalten eines ersten Satzes von ersten lonosphärenverzögerungsdifferentialen, welche
den entlang der durch die erste und zweite Basisstation ausgebildeten Basislinie empfangenen
Satellitensignalen zugeordnet sind,
Erhalten eines zweiten Satzes von zweiten lonosphärenverzögerungsdifferentialen, welche
den entlang der durch die erste und dritte Basisstation ausgebildeten Basislinie empfangenen
Satellitensignalen zugeordnet sind, und
Erzeugen von Korrekturen für ein oder mehrere aus den Residuen, wobei die Korrekturen
in Beziehung stehen mit dem ersten Satz von ersten lonosphärenverzögerungsdifferentialen,
dem zweiten Satz von zweiten Ionosphärenverzögerungsdifferentialen, den Standorten
der Basisstationen und einem abgeschätzten Standort der Erkundungsstation; und
Modifizieren des einen oder der mehreren aus den Residuen mit den Korrekturen.
17. Verfahren nach Anspruch 16, wobei die Korrektur für die Residuen, welche einem Satelliten
"s" in einem oder beiden von dem zweiten Satz von Residuen und dem zweiten Satz von
trägerphasenbasierten Residuen zugeordnet sind, in Beziehung steht zu der Größe
wobei
das einem Satelliten "s" zugeordnete erste lonosphärenverzögerungsdifferential ist,
und
ein abgeschätztes lonosphärenverzögerungsdifferential ist, welches einem Satelliten
"s" zugeordnet ist, entlang der Basislinie zwischen der Erkundungsstation und ersten
Basisstation.
18. Verfahren nach Anspruch 16, wobei die Korrektur für die Residuen, welche einem Satelliten
"s" in einem oder beiden von dem dritten Satz von Residuen und dem dritten Satz von
trägerphasenbasierten Residuen zugeordnet sind, in Beziehung steht zu der Größe
wobei
das einem Satelliten "s" zugeordnete zweite Ionosphärenverzögerungsdifferential ist,
und
ein abgeschätztes lonosphärenverzögerungsdifferential ist, welches einem Satelliten
"s" zugeordnet ist, entlang der Basislinie zwischen der Erkundungsstation und ersten
Basisstation.
19. Verfahren nach Anspruch 16, wobei das lonosphärenverzögerungsdifferential aus dem
ersten Satz und zugeordnet Satellit "s" bezeichnet werden kann als
wobei das lonosphärenverzögerungsdifferential aus dem zweiten Satz und zugeordnet
Satellit "s" bezeichnet werden kann als
wobei die Standorte der ersten, zweiten und dritten Basisstationen durch Vektoren
X
1, X
2 und X
3 repräsentiert werden können, und wobei der abgeschätzte Standort der Erkundungsstation
durch
X0,k repräsentiert werden kann,
wobei die Korrekturen für ein oder mehrere aus den Residuen, welche einem Satelliten
"s" zugeordnet sind, in Beziehung stehen zu einer Größe
wobei
wobei α und β Konstanten sind, welche die Beziehungen erfüllen:
wobei eine Schreibweise {
*}
n die Komponente der in Klammern gesetzten Größe entlang der Nordrichtung bezeichnet,
wobei eine Schreibweise {*}
e die Komponente der in Klammern gesetzten Größe entlang der Ostrichtung bezeichnet.
20. Verfahren nach Anspruch 19, wobei die Korrektur der einem Satelliten "s" zugeordneten
Residuen, in einem oder beiden aus dem zweiten Satz von Residuen und dem zweiten Satz
von trägerphasenbasierten Residuen, in Beziehung steht mit der Größe
wobei
das erste einem Satelliten "s" zugeordnete lonosphärenverzögerungsdifferential ist.
21. Verfahren nach Anspruch 19, wobei die Korrektur des einem Satelliten "s" zugeordneten
Residuums, in einem oder beiden aus den dritten Satz von Residuen und dem dritten
Satz von trägerphasenbasierten Residuen, in Beziehung steht mit der Größe
wobei
das zweite einem Satelliten "s" zugeordnete lonosphärenverzögerungsdifferential ist.
22. Verfahren nach Anspruch 16, ferner umfassend die Schritte:
Modifizieren eines oder mehrerer der obigen Residuen, um abhängig von Effekten zweiter
Ordnung in den lonosphärenverzögerungskorrekturen zu sein, welche an den Basislinien
appliziert werden, welche der Erkundungsstation zugeordnet sind, und
Erzeugen einer Abschätzung der Effekte zweiter Ordnung, und
wobei Schritt (g) die Abschätzung des Standortes der Erkundungsstation ferner aus
den abgeschätzten Effekten zweiter Ordnung erzeugt.
23. Verfahren nach Anspruch 16, wobei das Verfahren den ersten Satz von ersten lonosphärenverzögerungsdifferentialen
und den zweiten Satz von zweiten lonosphärenverzögerungsdifferentialen aus mindestens
den Navigationsdaten erzeugt, welches es von den Basisstationen empfängt.
24. Verfahren nach Anspruch 16, ferner umfassend die Schritte:
Erzeugen einer Initialabschätzung des ersten Satzes von ersten lonosphärenverzögerungsdifferentialen,
welche den entlang der durch die erste und zweite Basisstation ausgebildeten Basislinie
empfangenen Satellitensignalen zugeordnet sind;
Erzeugen einer Initialabschätzung eines zweiten Satzes von zweiten lonosphärenverzögerungsdifferentialen,
welche den entlang der durch die erste und dritte Basisstation ausgebildeten Basislinie
empfangenen Satellitensignalen zugeordnet sind;
Erzeugen einer Initialabschätzung eines dritten Satzes von dritten lonosphärenverzögerungsdifferentialen,
welche den entlang der durch die zweite und dritte Basisstation ausgebildeten Basislinie
empfangenen Satellitensignalen zugeordnet sind; und
Erzeugen finaler Abschätzungen der lonosphärenverzögerungsdifferentiale, sodass die
Summe der finalen Abschätzung der ersten, zweiten und dritten lonosphärenverzögerungsdifferentiale
für mindestens einen Satelliten "s", ringsum einer Schlaufe der Basisstationen, im
Wesentlichen null ist.
25. Verfahren nach Anspruch 7, wobei der Schritt eines Erhaltens des ersten Satzes von
Satellitenträgerphasenzyklusmehrdeutigkeiten den Schritt eines Erzeugens des ersten
Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten aus mindestens den Standorten
der Basisstationen und gemessener Satellitennavigationsdaten, wie durch die Basisstationen
empfangen, umfasst.
26. Verfahren nach Anspruch 8, wobei die Schritte eines Erhaltens der ersten und zweiten
Sätze von Satellitenträgerphasenzyklusmehrdeutigkeiten den Schritt eines Erzeugens
des ersten Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten aus mindestens
den Standorten der ersten und zweiten Basisstation und gemessenen Satellitennavigationsdaten,
wie durch die erste und zweite Basisstation empfangen, und den Schritt eines Erzeugens
des zweiten Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten aus mindestens
den Standorten der ersten und dritten Basisstation und gemessener Satellitennavigationsdaten,
wie durch die erste und dritte Basisstation empfangen, umfasst.
27. Verfahren nach Anspruch 26, ferner umfassend die Schritte eines Erzeugens eines dritten
Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten, welche der Basislinie zwischen
der zweiten und dritten Basisstation zugeordnet sind und Vergleichen der Summe von
den drei Sätzen von Satellitenträgerphasenmehrdeutigkeiten mit einem Wert von null,
ringsum einer Schlaufe der Basisstationen.
28. Computerprogramm, welches, wenn es auf einem Computerprozessor läuft, den Computerprozessor
dazu veranlasst, das Verfahren nach einem der vorhergehenden Ansprüche auszuführen.
29. Vorrichtung zum Abschätzen des Standortes einer Erkundungsstation (R) unter Verwendung
einer ersten Basisstation (B1) und einer zweiten Basisstation (B2), wobei die Vorrichtung
umfasst:
(a) Mittel zum Empfangen der Standorte der ersten Basisstation und der zweiten Basisstation;
(b) Mittel zum Empfangen gemessener Satellitennavigationsdaten, wie durch die Erkundungsstation,
die erste Basisstation und die zweite Basisstation empfangen;
(c) Mittel zum Erhalten eines ersten Zeitabstands, repräsentativ für einen Unterschied
zwischen einem ersten Abstand von einer wahren GPS-Zeit der Uhr der ersten Basisstation
und einem zweiten Abstand von einer wahren GPS-Zeit von der Uhr der zweiten Basisstation;
(d) Mittel zum Erzeugen eines ersten Satzes von Residuen von Differenzialnavigationsgleichungen,
welche einer ersten Basislinie (R-B1) zwischen der Erkundungsstation und der ersten
Basisstation zugeordnet sind, wobei die Residuen in Beziehung stehen mit den von der
Erkundungsstation und der ersten Basisstation empfangenen gemessenen Satellitennavigationsdaten,
den Standorten der Satelliten und den Standorten der Erkundungsstation und der ersten
Basisstation;
(e) Mittel zum Erzeugen eines zweiten Satzes von Residuen von Differenzialnavigationsgleichungen,
welche einer zweiten Basislinie (R-B2) zwischen der Erkundungsstation und der zweiten
Basisstation zugeordnet sind, wobei die Residuen in Beziehung stehen mit den von der
Erkundungsstation und der zweiten Basisstation empfangenen gemessenen Satellitennavigationsdaten,
den Standorten der Satelliten und den Standorten der Erkundungsstation und der zweiten
Basisstation; und
(f) Mittel zum Substituieren, innerhalb des zweiten Satzes von Residuen, eines unbekannten
Zeitabstands, welcher der zweiten Basislinie (R-B2) zugeordnet ist, mit einem Wert,
welcher aus einer Summe des ersten Zeitabstands und eines Zeitabstands, welcher der
ersten Basislinie (R-B1) zugeordnet ist, zusammengesetzt ist; und
(g) Mittel zum Erzeugen, dem Substitutionsschritt von (f) nachfolgend, eine Abschätzung
des Standortes der Erkundungsstation aus dem ersten Satz von Residuen, dem zweiten
Satz von Residuen und dem ersten Zeitabstand.
30. Vorrichtung nach Anspruch 29 ferner umfassend:
(h) Mittel zum Empfangen des Standortes einer dritten Basisstation;
(i) Mittel zum Empfangen gemessener Satellitennavigationsdaten, wie durch die dritte
Basisstation empfangen;
(j) Mittel zum Erhalten eines zweiten Zeitabstands, repräsentativ für den Unterschied
zwischen dem ersten Abstand von einer wahren GPS-Zeit von der Uhr der ersten Basisstation
und einem dritten Abstand von einer wahren GPS-Zeit von der Uhr der dritten Basisstation;
(k) Mittel zum Erzeugen eines dritten Satzes von Residuen von Differenzialnavigationsgleichungen,
welche einer dritten Basislinie (R-B3) zwischen der Erkundungsstation und der dritten
Basisstation zugeordnet sind, wobei die Residuen in Beziehung stehen mit den von der
Erkundungsstation und der dritten Basisstation empfangenen Satellitennavigationsdaten,
den Standorten der Satelliten und den Standorten der Erkundungsstation und der dritten
Basisstation;
(I) Mittel zum Substituieren, innerhalb des dritten Satzes von Residuen, eines unbekannten
Zeitabstands, welcher der dritten Basislinie (R-B3) zugeordnet ist, mit einem Wert,
welcher aus einer Summe des zweiten Zeitabstands und einer Zeit, welche der ersten
Basislinie (R-B1) zugeordnet ist, zusammengesetzt ist; und
wobei das Mittel (g) zum Erzeugen, dem Substitutionsschritt (I) nachfolgend, der Abschätzung
des Standortes der Erkundungsstation die Abschätzung ferner aus dem dritten Satz von
Residuen und dem zweiten Zeitabstand erzeugt.
31. Vorrichtung nach Anspruch 29, wobei das Mittel (c) zum Erhalten des ersten Zeitabstands
ein Mittel für ein Erzeugen des ersten Zeitabstands umfasst.
32. Vorrichtung nach Anspruch 30, wobei das Mittel (c) zum Erhalten des ersten Zeitabstands
ein Mittel für ein Erzeugen des ersten Zeitabstands umfasst und wobei das Mittel (j)
zum Erhalten des zweiten Zeitabstands ein Mittel für ein Erzeugen des zweiten Zeitabstands
umfasst.
33. Vorrichtung nach Anspruch 32, ferner umfassend ein Mittel für ein Erzeugen eines dritten
Zeitabstands, repräsentativ für einen Zeitunterschied zwischen dem zweiten Abstand
von einer wahren GPS-Zeit von der Uhr der zweiten Basisstation und des dritten Abstands
von einer wahren GPS-Zeit von der Uhr der dritten Basisstation und ein Mittel zum
Vergleichen der Summe des ersten Zeitabstands, des zweiten Zeitabstands und des dritten
Zeitabstands, ringsum einer Schlaufe von den Basisstationen, mit dem Wert von null.
34. Vorrichtung nach Anspruch 29 oder Anspruch 30, wobei der erste und zweite Satz von
Residuen auf Pseudoabstandsdaten basieren und wobei die Vorrichtung ferner ein Mittel
für ein Erzeugen eines ersten Satzes von trägerphasenbasierten Residuen von Differenzialnavigationsgleichungen
für die erste Basislinie (R-B1) zwischen der Erkundungsstation und der ersten Basisstation
umfasst, wobei der erste Satz von trägerphasenbasierten Residuen in Bezug steht zu
mindestens den gemessenen Satellitenträgerphasendaten, welche durch die Erkundungsstation
und die erste Basisstation empfangen werden, den Standorten der Satelliten, und den
Standorten der Erkundungsstation und der ersten Basisstation; und
wobei das Mittel (g) zum Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus dem ersten Satz von trägerphasenbasierten Residuen erzeugt.
35. Vorrichtung nach Anspruch 34, ferner umfassend:
Mittel zum Erhalten eines ersten Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten,
welche der Basislinie zwischen der ersten und zweiten Basisstation zugeordnet sind;
Mittel zum Erzeugen eines zweiten Satzes von trägerphasenbasierten Residuen von Differenzialnavigationsgleichungen,
welche der zweiten Basislinie (R-B2) zwischen der Erkundungsstation und der zweiten
Basisstation zugeordnet sind, wobei der zweite Satz von trägerphasenbasierten Residuen
in Bezug steht mit mindestens den gemessenen Satellitenträgerphasendaten, welche durch
die Erkundungsstation und die zweite Basisstation empfangen werden, den Standorten
der Satelliten, und den Standorten der Erkundungsstation und der zweiten Basisstation;
und
wobei das Mittel (g) zum Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus dem zweiten Satz von trägerphasenbasierten Residuen und
dem ersten Satz von Satellitenphasenzyklusmehrdeutigkeiten erzeugt.
36. Vorrichtung nach Anspruch 35, wobei Anspruch 34 von Anspruch 30 abhängig ist, ferner
umfassend:
Mittel zum Erhalten eines zweiten Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten,
welcher der Basislinie zwischen der ersten und dritten Basisstation zugeordnet sind;
Mittel zum Erzeugen eines dritten Satzes von trägerphasenbasierten Residuen von Differenzialnavigationsgleichungen,
welche der dritten Basislinie (R-B3) zwischen der Erkundungsstation und der dritten
Basisstation zugeordnet sind, wobei der dritte Satz von trägerphasenbasierten Residuen
in Beziehung steht mindestens mit den gemessenen Satellitenträgerphasendaten, welche
durch die Erkundungsstation und die dritte Basisstation empfangen werden, den Standorten
der Satelliten, und den Standorten der Erkundungsstation und der dritten Basisstation;
und
wobei das Mittel (g) zum Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus dem dritten Satz von trägerphasenbasierten Residuen und
dem zweiten Satz von Satellitphasenzyklusmehrdeutigkeiten erzeugt.
37. Vorrichtung nach Anspruch 32, ferner umfassend ein Mittel für ein Erzeugen eines ersten
Satzes von Fließkommamehrdeutigkeiten für die Basislinie zwischen der Erkundungsstation
und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten Residuen und
mindestens einem aus den Sätzen von Residuen, welche auf Pseudoabstandsdaten basieren;
und
wobei das Mittel (g) für ein Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus dem ersten Satz von Fließkommamehrdeutigkeiten erzeugt.
38. Vorrichtung nach Anspruch 34, ferner umfassend:
Mittel zum Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie
zwischen der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen und mindestens einem aus den Sätzen von Residuen, welche auf Pseudoabstandsdaten
basieren; und
Mittel zum Erzeugen eines ersten Satzes von Fest-Integer-Fließkommamehrdeutigkeiten
für die Basislinie zwischen der Erkundungsstation und ersten Basisstation aus dem
ersten Satz von Fließkommamehrdeutigkeiten;
wobei das Mittel (g) für ein Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus dem ersten Satz von Fest-Integer-Fließkommamehrdeutigkeiten
erzeugt.
39. Vorrichtung nach Anspruch 35, ferner umfassend:
Mittel zum Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie
zwischen der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von trägerphasenbasierten Residuen, dem ersten Satz von
Satellitenträgerphasenzyklusmehrdeutigkeiten, welche in Beziehung stehen zu der Basislinie
zwischen der ersten und zweiten Basisstation, und mindestens einem aus den Sätzen
von Residuen, welche auf Pseudoabstandsdaten basieren;
wobei das Mittel (g) für ein Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus dem ersten Satz von Fließkommamehrdeutigkeiten erzeugt.
40. Vorrichtung nach Anspruch 35, ferner umfassend:
Mittel zum Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie
zwischen der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von trägerphasenbasierten Residuen, dem ersten Satz von
Satellitenträgerphasenzyklusmehrdeutigkeiten, welche in Beziehung stehen zu der Basislinie
zwischen der ersten und zweiten Basisstation, und mindestens einem aus den Sätzen
von Residuen, welche auf Pseudoabstandsdaten basieren; und
Mittel zum Erzeugen eines ersten Satzes von Fest-Integer-Fließkommamehrdeutigkeiten
für die Basislinie zwischen der Erkundungsstation und ersten Basisstation aus dem
ersten Satz von Fließkommamehrdeutigkeiten;
wobei das Mittel (g) für ein Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus dem ersten Satz von Fest-Integer-Fließkommamehrdeutigkeiten
erzeugt.
41. Vorrichtung nach Anspruch 36, ferner umfassend:
Mittel zum Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie
zwischen der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von trägerphasenbasierten Residuen, dem ersten Satz von
Satellitenträgerphasenzyklusmehrdeutigkeiten, welche in Beziehung stehen zu der Basislinie
zwischen der ersten und zweiten Basisstation, dem dritten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von Satellitenträgerphasenzyklusmehrdeutigkeiten, welche
mit der Basislinie zwischen der ersten und zweiten Basisstation in Beziehung stehen,
und mindestens einem aus den Sätzen von Residuen, welche auf Pseudoabstandsdaten basieren;
wobei das Mittel (g) für ein Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus dem ersten Satz von Fließkommamehrdeutigkeiten erzeugt.
42. Vorrichtung nach Anspruch 36, ferner umfassend:
Mittel zum Erzeugen eines ersten Satzes von Fließkommamehrdeutigkeiten für die Basislinie
zwischen der Erkundungsstation und ersten Basisstation aus dem ersten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von trägerphasenbasierten Residuen, dem ersten Satz von
Satellitenträgerphasenzyklusmehrdeutigkeiten, welche mit der Basislinie zwischen der
ersten und zweiten Basisstation in Beziehung stehen, dem dritten Satz von trägerphasenbasierten
Residuen, dem zweiten Satz von Satellitenträgerphasenzyklusmehrdeutigkeiten, welche
mit der Basislinie zwischen der ersten und zweiten Basisstation in Beziehung stehen,
und mindestens einem aus den Sätzen von Residuen, welche auf Pseudoabstandsdaten basieren;
und
Mittel zum Erzeugen eines ersten Satzes von Fest-Integer-Fließkommamehrdeutigkeiten
für die Basislinie zwischen der Erkundungsstation und ersten Basisstation aus dem
ersten Satz von Fließkommamehrdeutigkeiten;
wobei das Mittel (g) für ein Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus dem ersten Satz von Fest-Integer-Fließkommamehrdeutigkeiten
erzeugt.
43. Vorrichtung nach einem der vorhergehenden Ansprüche 29-42, ferner umfassend:
Mittel zum Erhalten eines ersten Satzes von ersten lonosphärenverzögerungsdifferentialen,
welche den entlang einer zwischen der ersten und zweiten Basisstation ausgebildeten
Basislinie empfangenen Satellitensignalen zugeordnet sind, und
Mittel zum Erzeugen von Korrekturen für ein oder mehrere aus den Residuen, wobei die
Korrekturen in Beziehung stehen mit dem ersten Satz von ersten lonosphärenverzögerungsdifferentialen,
den Standorten der ersten und zweiten Basisstation und einem abgeschätzten Standort
der Erkundungsstation; und
Mittel zum Modifizieren des einen oder der mehreren aus den Residuen mit den Korrekturen.
44. Vorrichtung nach Anspruch 36, ferner umfassend:
Mittel zum Erhalten eines ersten Satzes von ersten lonosphärenverzögerungsdifferentialen,
welche den entlang der durch die erste und zweite Basisstation ausgebildeten Basislinie
empfangenen Satellitensignalen zugeordnet sind,
Mittel zum Erhalten eines zweiten Satzes von zweiten lonosphärenverzögerungsdifferentialen,
welche den entlang der durch die erste und dritte Basisstation ausgebildeten Basislinie
empfangenen Satellitensignalen zugeordnet sind, und
Mittel zum Erzeugen von Korrekturen für ein oder mehrere aus den Residuen, wobei die
Korrekturen in Beziehung stehen mit dem ersten Satz von ersten lonosphärenverzögerungsdifferentialen,
dem zweiten Satz von zweiten lonosphärenverzögerungsdifferentialen, den Standorten
der Basisstationen und einem abgeschätzten Standort der Erkundungsstation; und
Mittel zum Modifizieren des einen oder der mehreren aus den Residuen mit den Korrekturen.
45. Vorrichtung nach Anspruch 44, wobei die Korrektur für die Residuen, welche einem Satelliten
"s" in einem oder beiden von dem zweiten Satz von Residuen und dem zweiten Satz von
trägerphasenbasierten Residuen zugeordnet sind, in Beziehung steht zu der Größe
wobei
das einem Satelliten "s" zugeordnete erste lonosphärenverzögerungsdifferential ist,
und
ein abgeschätztes lonosphärenverzögerungsdifferential ist, welches einem Satelliten
"s" zugeordnet ist, entlang der Basislinie zwischen der Erkundungsstation und ersten
Basisstation.
46. Vorrichtung nach Anspruch 44, wobei die Korrektur für die Residuen, welche einem Satelliten
"s" in einem oder beiden von dem dritten Satz von Residuen und dem dritten Satz von
trägerphasenbasierten Residuen zugeordnet sind, in Beziehung steht zu der Größe
wobei
das einem Satelliten "s" zugeordnete zweite lonosphärenverzögerungsdifferential ist,
und
ein abgeschätztes lonosphärenverzögerungsdifferential ist, welches einem Satelliten
"s" zugeordnet ist, entlang der Basislinie zwischen der Erkundungsstation und ersten
Basisstation.
47. Vorrichtung nach Anspruch 44, wobei das lonosphärenverzögerungsdifferential aus dem
ersten Satz und zugeordnet Satellit "s" bezeichnet werden kann als
wobei das lonosphärenverzögerungsdifferential aus dem zweiten Satz und zugeordnet
Satellit "s" bezeichnet werden kann als
wobei die Standorte der ersten, zweiten und dritten Basisstationen durch Vektoren
X
1, X
2 und X
3 repräsentiert werden können, und wobei der abgeschätzte Standort der Erkundungsstation
durch
X0,k repräsentiert werden kann,
wobei die Korrekturen für ein oder mehrere aus den Residuen, welche einem Satelliten
"s" zugeordnet sind, in Beziehung stehen zu einer Größe
wobei
wobei α und β Konstanten sind, welche die Beziehungen erfüllen:
wobei eine Schreibweise {*}
n die Komponente der in Klammern gesetzten Größe entlang der Nordrichtung bezeichnet,
wobei eine Schreibweise {*}
e die Komponente der in Klammern gesetzten Größe entlang der Ostrichtung bezeichnet.
48. Vorrichtung nach Anspruch 44, wobei die Korrektur der einem Satellit "s" zugeordneten
Residuen, in einem oder beiden aus dem zweiten Satz von Residuen und dem zweiten Satz
von trägerphasenbasierten Residuen, in Beziehung steht mit der Größe
wobei
das erste einem Satelliten "s" zugeordnete lonosphärenverzögerungsdifferential ist.
49. Vorrichtung nach Anspruch 44, wobei die Korrektur des einem Satelliten "s" zugeordneten
Residuums, in einem oder beiden aus dem dritten Satz von Residuen und dem dritten
Satz von trägerphasenbasierten Residuen, in Beziehung steht mit der Größe
wobei
das zweite einem Satelliten "s" zugeordnete lonosphärenverzögerungsdifferential ist.
50. Vorrichtung nach Anspruch 43, ferner umfassend:
Mittel zum Modifizieren eines oder mehrerer der obigen Residuen, um abhängig von Effekten
zweiter Ordnung in den lonosphärenverzögerungskorrekturen zu sein, welche an den Basislinien
appliziert werden, welche der Erkundungsstation zugeordnet sind, und
Mittel zum Erzeugen einer Abschätzung der Effekte zweiter Ordnung, und
wobei das Mittel (i) für ein Erzeugen der Abschätzung des Standortes der Erkundungsstation
die Abschätzung ferner aus den abgeschätzten Effekten zweiter Ordnung erzeugt.
51. Vorrichtung nach Anspruch 43, wobei die Vorrichtung den ersten Satz von ersten lonosphärenverzögerungsdifferentialen
und den zweiten Satz von zweiten lonosphärenverzögerungsdifferentialen aus mindestens
den Navigationsdaten erzeugt, welches sie von den Basisstationen empfängt.
52. Vorrichtung nach Anspruch 43, ferner umfassend:
Mittel zum Erzeugen einer Initialabschätzung des ersten Satzes von ersten lonosphärenverzögerungsdifferentialen,
welche den entlang der durch die erste und zweite Basisstation ausgebildeten Basislinie
empfangenen Satellitensignalen zugeordnet sind;
Mittel zum Erzeugen einer Initialabschätzung eines zweiten Satzes von zweiten lonosphärenverzögerungsdifferentialen,
welche den entlang der durch die erste und dritte Basisstation ausgebildeten Basislinie
empfangenen Satellitensignalen zugeordnet sind;
Mittel zum Erzeugen einer Initialabschätzung eines dritten Satzes von dritten lonosphärenverzögerungsdifferentialen,
welche den entlang der durch die zweite und dritte Basisstation ausgebildeten Basislinie
empfangenen Satellitensignalen zugeordnet sind; und
Mittel zum Erzeugen finaler Abschätzungen der lonosphärenverzögerungsdifferentiale,
sodass die Summe der finalen Abschätzung der ersten, zweiten und dritten lonosphärenverzögerungsdifferentiale
für mindestens einen Satelliten "s", ringsum einer Schlaufe der Basisstationen, im
Wesentlichen null ist.
53. Vorrichtung nach Anspruch 35, wobei das Mittel für ein Erhalten des ersten Satzes
von Satellitenträgerphasenzyklusmehrdeutigkeiten ein Mittel für ein Erzeugen des ersten
Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten aus mindestens den Standorten
der Basisstationen und gemessener Satellitennavigationsdaten, wie durch die Basisstationen
empfangen, umfasst.
54. Vorrichtung nach Anspruch 36, wobei das Mittel für ein Erhalten der ersten und zweiten
Sätze von Satellitenträgerphasenzyklusmehrdeutigkeiten ein Mittel für ein Erzeugen
des ersten Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten aus mindestens
den Standorten der ersten und zweiten Basisstation und gemessenen Satellitennavigationsdaten,
wie durch die erste und zweite Basisstation empfangen, und ein Mittel für ein Erzeugen
des zweiten Satzes von Satellitenträgerphasenzyklusmehrdeutigkeiten aus mindestens
den Standorten der ersten und dritten Basisstation und gemessener Satellitennavigationsdaten,
wie durch die erste und dritte Basisstation empfangen, umfasst.
1. Procédé d'estimation de l'emplacement d'une station itinérante (R) à l'aide d'une
première station de base (B1) et d'une deuxième station de base (B2), le procédé comprenant
le fait de :
(a) recevoir (202) des emplacements connus de la première station de base et de la
deuxième station de base ;
(b) recevoir (206) des données de navigation par satellite mesurées telles que reçues
par la station itinérante, la première station de base, et la deuxième station de
base ;
(c) obtenir (208) un premier décalage temporel représentant une différence entre un
premier décalage par rapport à un temps GPS réel de l'horloge de la première station
de base et un deuxième décalage par rapport au temps GPS réel de l'horloge de la deuxième
station de base ;
(d) de générer (214) un premier ensemble de résidus d'équations de navigation différentielles
associé à une première ligne de base (R-B1) entre la station itinérante et la première
station de base, les résidus étant liés aux données de navigation par satellite mesurées
qui sont reçues par la station itinérante et la première station de base, les emplacements
des satellites, et les emplacements de la station itinérante et de la première station
de base ;
(e) générer (214) un deuxième ensemble de résidus d'équations de navigation différentielles
associé à une deuxième ligne de base (R-B2) entre la station itinérante et la deuxième
station de base, les résidus étant liés aux données de navigation par satellite mesurées
qui sont reçues par la station itinérante et la deuxième station de base, les emplacements
des satellites, et les emplacements de la station itinérante et de la deuxième station
de base ;
(f) remplacer, dans le deuxième ensemble de résidus, un décalage temporel inconnu
associé à la deuxième ligne de base (R-B2) par une valeur composée d'une somme du
premier décalage temporel et d'un décalage temporel associé à la première ligne de
base (R- B1) ; et
(g) générer (218), à la suite de l'étape de substitution (f), une estimation de l'emplacement
de la station itinérante à partir du premier ensemble de résidus, du deuxième ensemble
de résidus et du premier décalage temporel.
2. Procédé de la revendication 1, comprenant en outre les étapes consistant à :
(h) recevoir (202) l'emplacement d'une troisième station de base (B3) ;
(i) recevoir (206) des données de navigation par satellite mesurées telles que reçues
par la troisième station de base ; et
(j) obtenir (208) un deuxième décalage temporel représentant la différence entre le
premier décalage temporel par rapport au temps GPS réel de l'horloge de la première
station de base et un troisième décalage par rapport au temps GPS réel de l'horloge
de la troisième station de base ;
(k) générer (214) un troisième ensemble de résidus d'équations de navigation différentielles
associé à une troisième ligne de base (R-B3) entre la station itinérante et la troisième
station de base, les résidus étant liés aux données de navigation par satellite reçues
par la station itinérante et la troisième station de base, les emplacements des satellites,
et les emplacements de la station itinérante et de la troisième station de base ;
(1) remplacer, dans le troisième ensemble de résidus, un décalage temporel inconnu
associé à la troisième ligne de base (R-B3) par une valeur composée d'une somme du
deuxième décalage temporel et un décalage temporel associé à la première ligne de
base (R- B1) ; et
dans lequel l'étape (g) génère, à la suite de l'étape de substitution (1), l'estimation
de l'emplacement de la station itinérante davantage à partir du troisième ensemble
de résidus et du deuxième décalage temporel.
3. Procédé de la revendication 1, dans lequel l'étape (c) comprend l'étape de génération
du premier décalage temporel.
4. Procédé de la revendication 2, dans lequel l'étape (c) comprend l'étape de génération
du premier décalage temporel et dans lequel l'étape (j) comprend l'étape de génération
du deuxième décalage temporel.
5. Procédé de la revendication 4, comprenant en outre les étapes consistant à générer
un troisième décalage temporel représentant une différence entre le deuxième décalage
par rapport au temps GPS réel de l'horloge de la deuxième station et le troisième
décalage par rapport au temps GPS réel de l'horloge de la troisième station de base,
et à comparer la somme du premier décalage temporel, du deuxième décalage temporel
et du troisième décalage temporel autour d'une boucle des stations de base à la valeur
zéro.
6. Procédé de la revendication 1 ou 2, dans lequel les premier et deuxième ensembles
de résidus sont basés sur des données de pseudo-distance, et dans lequel ledit procédé
comprend en outre l'étape consistant à générer un premier ensemble de résidus basés
sur la phase de porteuse d'équations de navigation différentielles pour la première
ligne de base (R-B1) entre la station itinérante et la première station de base, le
premier ensemble de résidus basés sur la phase de porteuse étant lié à au moins les
données de phase de porteuse de satellite mesurées qui sont reçues par la station
itinérante et la première station de base, les emplacements des satellites, et les
emplacements de la station itinérante et de la première station de base ; et
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir du premier ensemble de résidus basés sur la phase de porteuse.
7. Procédé de la revendication 6, comprenant en outre les étapes consistant à :
obtenir un premier ensemble d'ambiguïtés de cycle de phase de porteuse de satellite
associé à la ligne de base entre les première et deuxième stations de base ;
générer un deuxième ensemble de résidus basés sur la phase de porteuse d'équations
de navigation différentielles associé à la deuxième ligne de base (R-B2) entre la
station itinérante et la deuxième station de base, le deuxième ensemble de résidus
basés sur la phase de porteuse étant lié à au moins les données de phase de porteuse
de satellite mesurées qui sont reçues par la station itinérante et la deuxième station
de base, les emplacements des satellites, et les emplacements de la station itinérante
et de la deuxième station de base ; et
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir du deuxième ensemble de résidus basés sur la phase de porteuse
et du premier ensemble d'ambiguïtés de cycle de phase de satellite.
8. Procédé de la revendication 7, dans lequel revendication 6 est dépendante de la revendication
2, comprenant en outre les étapes consistant à :
obtenir un deuxième ensemble d' ambiguïtés de cycle de phase de porteuse de satellite
associé à la ligne de base entre les première et troisième stations de base ;
générer un troisième ensemble de résidus basés sur la phase de porteuse d'équations
de navigation différentielles associé à la troisième ligne de base (R-B3) entre la
station itinérante et la troisième station de base, le troisième ensemble de résidus
basés sur la phase de porteuse étant lié à au moins les données de phase de porteuse
de satellite mesurées qui sont reçues par la station itinérante et la troisième station
de base, les emplacements des satellites, et les emplacements de la station itinérante
et de la troisième station de base ; et
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir du troisième ensemble de résidus basés sur la phase de porteuse
et du deuxième ensemble d'ambiguïtés de cycle de phase de satellite.
9. Procédé de la revendication 6, comprenant en outre l'étape consistant à générer un
premier ensemble d'ambiguïtés flottantes pour la ligne de base entre la station itinérante
et la première station de base à partir du premier ensemble de résidus basés sur la
phase de porteuse et d'au moins l'un des ensembles de résidus basés sur des données
de pseudo-distance ; et
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir du premier ensemble d'ambiguïtés flottantes.
10. Procédé de la revendication 6, comprenant en outre les étapes consistant à :
générer un premier ensemble d'ambiguïtés flottantes pour la ligne de base entre la
station itinérante et la première station de base à partir du premier ensemble de
résidus basés sur la phase de porteuse et d'au moins l'un des ensembles de résidus
basés sur des données de pseudo-distance; et
générer un premier ensemble d'ambiguïtés flottantes d'entier fixe pour la ligne de
base entre la station itinérante et la première station de base à partir du premier
ensemble d'ambiguïtés flottantes ;
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir du premier ensemble d'ambiguïtés flottantes d'entier fixe.
11. Procédé de la revendication 7, comprenant en outre l'étape consistant à :
générer un premier ensemble d'ambiguïtés flottantes pour la ligne de base entre la
station itinérante et la première station de base à partir du premier ensemble de
résidus basés sur la phase de porteuse, du deuxième ensemble de résidus basés sur
la phase de porteuse, du premier ensemble d'ambiguïtés de cycle de phase de porteuse
de satellite lié à la ligne de base entre les première et deuxième stations de base,
et d'au moins l'un des ensembles de résidus basés sur des données de pseudo-distance
;
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir du premier ensemble d'ambiguïtés flottantes.
12. Procédé de la revendication 6, comprenant en outre les étapes consistant à :
générer un premier ensemble d'ambiguïtés flottantes pour la ligne de base entre la
station itinérante et la première station de base à partir du premier ensemble de
résidus basés sur la phase de porteuse, du deuxième ensemble de résidus basés sur
la phase de porteuse, du premier ensemble d'ambiguïtés de cycle de phase de porteuse
de satellite lié à la ligne de base entre les première et deuxième stations de base,
et d'au moins l'un des ensembles de résidus basés sur des données de pseudo-distance
;
générer un premier ensemble d'ambiguïtés flottantes d'entier fixe pour la ligne de
base entre la station itinérante et la première station de base à partir du premier
ensemble d'ambiguïtés flottantes ;
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir du premier ensemble d'ambiguïtés flottantes d'entier fixe.
13. Procédé de la revendication 8, comprenant en outre l'étape consistant à :
générer un premier ensemble d'ambiguïtés flottantes pour la ligne de base entre la
station itinérante et la première station de base à partir du premier ensemble de
résidus basés sur la phase de porteuse, du deuxième ensemble de résidus basés sur
la phase de porteuse, du premier ensemble d'ambiguïtés de cycle de phase de porteuse
de satellite lié à la ligne de base entre les première et deuxième stations de base,
du troisième ensemble de résidus basés sur la phase de porteuse, du deuxième ensemble
d'ambiguïtés de cycle de phase de porteuse de satellite lié à la ligne de base entre
les première et deuxième stations de base, et d'au moins l'un des ensembles de résidus
basés sur des données de pseudo-distance ;
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir du premier ensemble d'ambiguïtés flottantes.
14. Procédé de la revendication 8, comprenant en outre les étapes consistant à :
générer un premier ensemble d'ambiguïtés flottantes pour la ligne de base entre la
station itinérante et la première station de base à partir du premier ensemble de
résidus basés sur la phase de porteuse, du deuxième ensemble de résidus basés sur
la phase de porteuse, du premier ensemble d'ambiguïtés de cycle de phase de porteuse
de satellite lié à la ligne de base entre les première et deuxième stations de base,
du troisième ensemble de résidus basés sur la phase de porteuse, du deuxième ensemble
d'ambiguïtés de cycle de phase de porteuse de satellite lié à la ligne de base entre
les première et deuxième stations de base, et d'au moins l'un des ensembles de résidus
basés sur des données de pseudo-distance ;
générer un premier ensemble d'ambiguïtés flottantes d'entier fixe pour la ligne de
base entre la station itinérante et la première station de base à partir du premier
ensemble d'ambiguïtés flottantes ;
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir du premier ensemble d'ambiguïtés flottantes d'entier fixe.
15. Procédé selon l'une des revendications précédentes, comprenant en outre les étapes
consistant à :
obtenir un premier ensemble de premiers différentiels de retard ionosphérique associé
aux signaux satellites reçus le long de la ligne de base formée par les première et
deuxième stations de base, et
générer des corrections apportées à un ou plusieurs des résidus, les corrections étant
liées au premier ensemble de premiers différentiels de retard ionosphérique, aux emplacements
des première et deuxième stations de base, et à un emplacement estimé de la station
itinérante ; et
modifier ledit un ou plusieurs des résidus avec lesdites corrections.
16. Procédé selon la revendication 8, comprenant en outre les étapes consistant à :
obtenir un premier ensemble de premiers différentiels de retard ionosphérique associé
aux signaux satellites reçus le long de la ligne de base formée par les première et
deuxième stations de base,
obtenir un deuxième ensemble de deuxièmes différentiels de retard ionosphérique associé
aux signaux satellites reçus le long de la ligne de base formée par les première et
troisième stations de base, et
générer des corrections apportées à un ou plusieurs des résidus, les corrections étant
liées au premier ensemble de premiers différentiels de retard ionosphérique, au deuxième
ensemble de deuxièmes différentiels de retard ionosphérique, aux emplacements des
stations de base, et à un emplacement estimé de la station itinérante ; et
modifier ledit un ou plusieurs des résidus avec lesdites corrections.
17. Procédé de la revendication 16, dans lequel la correction apportée aux résidus associés
au satellite "s" dans le deuxième ensemble de résidus et/ou le deuxième ensemble de
résidus basés sur la phase de porteuse est liée à la quantité
où
est le premier différentiel de retard ionosphérique associé au satellite "s", et
est un différentiel de retard ionosphérique estimé associé au satellite "s" le long
de la ligne de base entre la station itinérante et la première station de base.
18. Procédé de la revendication 16, dans lequel la correction apportée aux résidus associés
au satellite "s" dans le troisième ensemble de résidus et/ou le troisième ensemble
de résidus basés sur la phase de porteuse est liée à la quantité
où
est le deuxième différentiel de retard ionosphérique associé au satellite "s", et
est un différentiel de retard ionosphérique estimé associé au satellite "s" le long
de la ligne de base entre la station itinérante et la première station de base.
19. Procédé de la revendication 16, dans lequel le différentiel de retard ionosphérique
à partir du premier ensemble et associé au satellite "s" peut être indiqué par
dans lequel le différentiel de retard ionosphérique à partir du deuxième ensemble
et associé au satellite "s" peut être indiqué par
dans lequel les emplacements des première, deuxième et troisième stations de base
peuvent être représentés par les vecteurs X
1, X
2 et X
3, et dans lequel l'emplacement estimé de la station itinérante peut être représenté
par
X0,k,
dans lequel les corrections apportées à un ou plusieurs des résidus associés au satellite
"s" sont liées à une quantité
où
où α et β sont des constantes qui satisfont les relations :
où la notation {*}
n indique la composante de la quantité entre crochets le long de la direction nord,
où la notation {*}
e indique la composante de la quantité entre crochets le long de la direction est.
20. Procédé de la revendication 19, dans lequel la correction apportée aux résidus associés
au satellite "s" dans le deuxième ensemble de résidus et/ou le deuxième ensemble de
résidus basés sur la phase de porteuse est liée à la quantité
où
est le premier différentiel de retard ionosphérique associé au satellite "s".
21. Procédé de la revendication 19, dans lequel la correction apportée au résidu associé
au satellite "s" dans le troisième ensemble de résidus et/ou le troisième ensemble
de résidus basés sur la phase de porteuse est liée à la quantité
où
est le deuxième différentiel de retard ionosphérique associé au satellite "s".
22. Procédé selon la revendication 16, comprenant en outre les étapes consistant à :
modifier un ou plusieurs des résidus ci-dessus pour qu'il(s) dépende(nt) des deuxième
effets d'ordre dans les corrections de retard ionosphérique appliquées aux lignes
de base associées à la station itinérante, et
générer une estimation des deuxièmes effets d'ordre, et
dans lequel l'étape (g) génère l'estimation de l'emplacement de la station itinérante
davantage à partir des deuxièmes effets d'ordre estimés.
23. Procédé selon la revendication 16, dans lequel le procédé génère le premier ensemble
de premiers différentiels de retard ionosphérique et le deuxième ensemble de deuxièmes
différentiels de retard ionosphérique à partir d'au moins les données de navigation
qu'il reçoit à partir des stations de base.
24. Procédé selon la revendication 16, comprenant en outre les étapes consistant à :
générer une estimation initiale du premier ensemble de premiers différentiels de retard
ionosphérique associés aux signaux satellites reçus le long de la ligne de base formée
par les première et deuxième stations de base ;
générer une estimation initiale du deuxième ensemble de deuxièmes différentiels de
retard ionosphérique associés aux signaux satellites reçus le long de la ligne de
base formée par les première et troisième stations de base ;
générer une estimation initiale d'un troisième ensemble de troisièmes différentiels
de retard ionosphérique associés aux signaux satellites reçus le long de la ligne
de base formée par les deuxième et troisième stations de base ; et
générer des estimations finales des différentiels de retard ionosphérique de telle
sorte que la somme des estimations finales des premier, deuxième et troisième différentiels
de retard ionosphérique pour au moins un satellite "s" autour d'une boucle des stations
de base soit substantiellement égale à zéro.
25. Procédé de la revendication 7, dans lequel l'étape d'obtention du premier ensemble
d'ambiguïtés de cycle de phase de porteuse de satellite comprend l'étape de génération
du premier ensemble d'ambiguïtés de cycle de phase de porteuse de satellite à partir
d'au moins les emplacements des stations de base et les données de navigation par
satellite mesurées telles que reçues par les stations de base.
26. Procédé de la revendication 8, dans lequel l'étape d'obtention des premier et deuxième
ensembles d'ambiguïtés de cycle de phase de porteuse de satellite comprend l'étape
de génération du premier ensemble d'ambiguïtés de cycle de phase de porteuse de satellite
à partir d'au moins les emplacements des première et deuxième stations de base et
les données de navigation par satellite mesurées telles que reçues par les première
et deuxième stations de base, et l'étape de génération du deuxième ensemble d'ambiguïtés
de cycle de phase de porteuse de satellite à partir d'au moins les emplacements des
première et troisième stations de base et les données de navigation par satellite
mesurées telles que reçues par les première et troisième stations de base.
27. Procédé de la revendication 26 comprenant en outre les étapes consistant à générer
un troisième ensemble d'ambiguïtés de cycle de phase de porteuse de satellite associé
à la ligne de base entre les deuxième et troisième stations de base, et à comparer
la somme des trois ensembles d'ambiguïtés de phase de porteuse de satellite autour
d'une boucle des stations de base à la valeur zéro.
28. Programme informatique qui, lorsqu'il est exécuté sur un processeur informatique,
amène le processeur informatique à réaliser le procédé de l'une des revendications
précédentes.
29. Appareil destiné à estimer l'emplacement d'une station itinérante (R) à l'aide d'une
première station de base (B1) et d'une deuxième station de base (B2), l'appareil comprenant
:
(a) un moyen pour recevoir les emplacements de la première station de base et de la
deuxième station de base ;
(b) un moyen pour recevoir des données de navigation par satellite mesurées telles
que reçues par la station itinérante, la première station de base, et la deuxième
station de base ;
(c) un moyen pour obtenir un premier décalage temporel représentant une différence
entre un premier décalage par rapport au temps GPS réel de l'horloge de la première
station de base et un deuxième décalage par rapport au temps GPS réel de l'horloge
de la deuxième station de base ;
(d) un moyen pour générer un premier ensemble de résidus d'équations de navigation
différentielles associé à une première ligne de base (R-B1) entre la station itinérante
et la première station de base, les résidus étant liés aux données de navigation par
satellite mesurées qui sont reçues par la station itinérante et la première station
de base, les emplacements des satellites, et les emplacements de la station itinérante
et de la première station de base ;
(e) un moyen pour générer un deuxième ensemble de résidus d'équations de navigation
différentielles associé à une deuxième ligne de base (R-B2) entre la station itinérante
et la deuxième station de base, les résidus étant liés aux données de navigation par
satellite mesurées qui sont reçues par la station itinérante et la deuxième station
de base, les emplacements des satellites, et les emplacements de la station itinérante
et de la deuxième station de base ; et
(f) un moyen pour remplacer, dans le deuxième ensemble de résidus, un décalage temporel
inconnu associé à la deuxième ligne de base (R-B2) par une valeur composée d'une somme
du premier décalage temporel et d'un décalage temporel associé à la première ligne
de base (R-B1) ; et
(g) un moyen pour générer, à la suite de la substitution de l'étape (f), une estimation
de l'emplacement de la station itinérante à partir du premier ensemble de résidus,
du deuxième ensemble de résidus et du premier décalage temporel.
30. Appareil de la revendication 29 comprenant en outre :
(h) un moyen pour recevoir l'emplacement de la troisième station de base;
(i) un moyen pour recevoir des données de navigation par satellite mesurées telles
que reçues par la troisième station de base ;
(j) un moyen pour obtenir un deuxième décalage temporel représentant la différence
entre le premier décalage par rapport au temps GPS réel de l'horloge de la première
station de base et un troisième décalage par rapport au temps GPS réel de l'horloge
de la troisième station de base ;
(k) un moyen pour générer un troisième ensemble de résidus d'équations de navigation
différentielles associé à une troisième ligne de base (R-B3) entre la station itinérante
et la troisième station de base, les résidus étant liés aux données de navigation
par satellite reçues par la station itinérante et la troisième station de base, les
emplacements des satellites, et les emplacements de la station itinérante et de la
troisième station de base ;
(1) un moyen pour remplacer, dans le troisième ensemble de résidus, un décalage temporel
inconnu associé à la troisième ligne de base (R-B3) par une valeur composée d'une
somme du deuxième décalage temporel et d'un temps associé à la première base (R-B1)
; et
dans lequel le moyen (g) de génération, à la suite de l'étape de substitution (1),
de l'estimation de l'emplacement de la station itinérante génère l'estimation davantage
à partir du troisième ensemble de résidus et du deuxième décalage temporel.
31. Appareil de la revendication 29, dans lequel le moyen (c) d'obtention du premier décalage
temporel comprend un moyen de génération du premier décalage temporel.
32. Appareil de la revendication 30, dans lequel le moyen (c) d'obtention du premier décalage
temporel comprend un moyen de génération du premier décalage temporel et dans lequel
le moyen (j) d'obtention du deuxième décalage temporel comprend un moyen de génération
du deuxième décalage temporel.
33. Appareil de la revendication 32, comprenant en outre un moyen pour générer un troisième
décalage temporel représentant la différence temporelle entre le deuxième décalage
par rapport au temps GPS réel de l'horloge de la deuxième station de base et le troisième
décalage par rapport au temps GPS réel de l'horloge de la troisième station de base,
et un moyen pour comparer la somme du premier décalage temporel, du deuxième décalage
temporel, et du troisième décalage temporel autour d'une boucle des stations de base
à la valeur zéro.
34. Appareil de la revendication 29 ou 30, dans lequel les premier et deuxième ensembles
de résidus sont basés sur des données de pseudo-distance, et dans lequel l'appareil
comprend en outre un moyen pour générer un premier ensemble de résidus basés sur la
phase de porteuse d'équations de navigation différentielles pour la première ligne
de base (R-B1) entre la station itinérante et la première station de base, le premier
ensemble de résidus basés sur la phase de porteuses étant lié à au moins les données
de phase de porteuse de satellite mesurées qui sont reçues par la station itinérante
et la première la station de base, les emplacements des satellites, et les emplacements
de la station itinérante et de la première station de base ; et
dans lequel le moyen (g) de génération de l'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir du premier ensemble de résidus basés
sur la phase de porteuse.
35. Appareil de la revendication 34 comprenant en outre :
un moyen pour obtenir un premier ensemble d'ambiguïtés de cycle de phase de porteuse
de satellite associé à la ligne de base entre les première et deuxième stations de
base ;
un moyen pour générer un deuxième ensemble de résidus basés sur la phase de porteuse
d'équations de navigation différentielles associé à la deuxième ligne de base (R-B2)
entre la station itinérante et la deuxième station de base, le deuxième ensemble de
résidus basés sur la phase de porteuse étant lié à au moins les données de phase de
porteuse de satellite mesurées qui sont reçues par la station itinérante et la deuxième
station de base, les emplacements des satellites, et les emplacements de la station
itinérante et de la deuxième station de base ; et
dans lequel le moyen (g) de génération de l'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir du deuxième ensemble de résidus
basés sur la phase de porteuse et du premier ensemble d'ambiguïtés de cycle de phase
de satellite.
36. Appareil de la revendication 35, dans lequel la revendication 34 est dépendante de
la revendication 30 comprenant en outre :
un moyen pour obtenir un deuxième ensemble d'ambiguïtés de cycle de phase de porteuse
de satellite associé à la ligne de base entre les première et troisième stations de
base ;
un moyen pour générer un troisième ensemble de résidus basés sur la phase de porteuse
d'équations de navigation différentielles associé à la troisième ligne de base (R-B3)
entre la station itinérante et la troisième station de base, le troisième ensemble
de résidus basés sur la phase de porteuse étant lié à au moins les données de phase
de porteuse de satellite mesurées qui sont reçues par la station itinérante et la
troisième station de base, les emplacements des satellites, et les emplacements de
la station itinérante et de la troisième station de base ; et
dans lequel le moyen (g) de génération de l'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir du troisième ensemble de résidus
basés sur la phase de porteuse et du deuxième ensemble d'ambiguïtés de cycle de phase
de satellite.
37. Appareil de la revendication 32, comprenant en outre un moyen pour générer un premier
ensemble d'ambiguïtés flottantes pour la ligne de base entre la station itinérante
et la première station de base à partir du premier ensemble de résidus basés sur la
phase de porteuse et d'au moins l'un des ensembles de résidus basés sur des données
de pseudo-distance; et
dans lequel le moyen (g) de génération de l'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir du premier ensemble d'ambiguïtés
flottantes.
38. Appareil de la revendication 34 comprenant en outre :
un moyen pour générer un premier ensemble d'ambiguïtés flottantes pour la ligne de
base entre la station itinérante et la première station de base à partir du premier
ensemble de résidus basés sur la phase de porteuse et d'au moins l'un des ensembles
de résidus basés sur des données de pseudo-distance; et
un moyen pour générer un premier ensemble d'ambiguïtés flottantes d'entier fixe pour
la ligne de base entre la station itinérante et la première station de base du premier
ensemble d'ambiguïtés flottantes ;
dans lequel le moyen (g) de génération d'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir du premier ensemble d'ambiguïtés
flottantes d'entier fixe.
39. Appareil de la revendication 35 comprenant en outre :
un moyen pour générer un premier ensemble d'ambiguïtés flottantes pour la ligne de
base entre la station itinérante et la première station de base à partir du premier
ensemble de résidus basés sur la phase de porteuse, du deuxième ensemble de résidus
basés sur la phase de porteuse, du premier ensemble d'ambiguïtés de cycle de phase
de porteuse de satellite lié à la ligne de base entre les première et deuxième stations
de base, et d'au moins l'un des ensembles de résidus basés sur des données de pseudo-distance
;
dans lequel le moyen (g) de génération de l'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir du premier ensemble d'ambiguïtés
flottantes.
40. Appareil de la revendication 35 comprenant en outre :
un moyen pour générer un premier ensemble d'ambiguïtés flottantes pour la ligne de
base entre la station itinérante et la première station de base à partir du premier
ensemble de résidus basés sur la phase de porteuse, du deuxième ensemble de résidus
basés sur la phase de porteuse, du premier ensemble d'ambiguïtés de cycle de phase
de porteuse de satellite lié à la ligne de base entre les première et deuxième stations
de base, et d'au moins l'un des ensembles de résidus basés sur des données de pseudo-distance
; et
un moyen pour générer un premier ensemble d'ambiguïtés flottantes d'entier fixe pour
la ligne de base entre la station itinérante et la première station de base à partir
du premier ensemble d'ambiguïtés flottantes ;
dans lequel le moyen (g) de génération de l'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir du premier ensemble d'ambiguïtés
flottantes d'entier fixe.
41. Appareil de la revendication 36 comprenant en outre :
un moyen pour générer un premier ensemble d'ambiguïtés flottantes pour la ligne de
base entre la station itinérante et la première station de base à partir du premier
ensemble de résidus basés sur la phase de porteuse, du deuxième ensemble de résidus
basés sur la phase de porteuse, du premier ensemble d'ambiguïtés de cycle de phase
de porteuse de satellite lié à la ligne de base entre les première et deuxième stations
de base, du troisième ensemble de résidus basés sur la phase de porteuse, du deuxième
ensemble d'ambiguïtés de cycle de phase de porteuse de satellite liés à la ligne de
base entre les première et deuxième stations de base, et d'au moins l'un des ensembles
de résidus basés sur des données de pseudo-distance ;
dans lequel le moyen (g) de génération de l'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir du premier ensemble d'ambiguïtés
flottantes.
42. Appareil de la revendication 36 comprenant en outre :
un moyen pour générer un premier ensemble d'ambiguïtés flottantes pour la ligne de
base entre la station itinérante et la première station de base à partir du premier
ensemble de résidus basés sur la phase de porteuse, du deuxième ensemble de résidus
basés sur la phase de porteuse, du premier ensemble d'ambiguïtés de cycle de phase
de porteuse de satellite lié à la ligne de base entre les première et deuxième stations
de base, du troisième ensemble de résidus basés sur la phase de porteuse, du deuxième
ensemble d'ambiguïtés de cycle de phase de porteuse de satellite lié à la ligne de
base entre les première et deuxième stations de base, et d'au moins l'un des ensembles
de résidus basés sur des données de pseudo-distance ; et
un moyen pour générer un premier ensemble d'ambiguïtés flottantes d'entier fixe pour
la ligne de base entre la station itinérante et la première station de base à partir
du premier ensemble d'ambiguïtés flottantes ;
dans lequel le moyen (g) de génération de l'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir du premier ensemble d'ambiguïtés
flottantes d'entier fixe.
43. Appareil selon l'une des revendications précédentes 29-42 comprenant en outre :
un moyen pour obtenir un premier ensemble de premiers différentiels de retard ionosphérique
associé aux signaux satellites reçus le long de la ligne de base formée par les première
et deuxième stations de base, et
un moyen pour générer des corrections apportées à un ou plusieurs des résidus, les
corrections étant liées au premier ensemble de premiers différentiels de retard ionosphérique,
aux emplacements des première et deuxième stations de base, et à un emplacement estimé
de la station itinérante ; et
un moyen pour modifier lesdits un ou plusieurs des résidus avec lesdites corrections.
44. Appareil selon la revendication 36 comprenant en outre :
un moyen pour obtenir un premier ensemble de premiers différentiels de retard ionosphérique
associé aux signaux satellites reçus le long de la ligne de base formée par les première
et deuxième stations de base,
un moyen pour obtenir un deuxième ensemble de deuxièmes différentiels de retard ionosphérique
associé aux signaux satellites reçus le long de la ligne de base formée par les première
et troisième stations de base, et
un moyen pour générer des corrections apportées à un ou plusieurs des résidus, les
corrections étant liées au premier ensemble de premiers différentiels de retard ionosphérique,
au deuxième ensemble de deuxièmes différentiels de retard ionosphérique, aux emplacements
des stations de base, et à un emplacement estimé de la station itinérante ; et
un moyen pour modifier lesdits un ou plusieurs des résidus avec lesdites corrections.
45. Appareil de la revendication 44, dans lequel la correction apportée aux résidus associés
au satellite "s" dans le deuxième ensemble de résidus et/ou le deuxième ensemble de
résidus basés sur la phase de porteuse est liée à la quantité
où
est le premier différentiel de retard ionosphérique associé au satellite "s", et
est un différentiel de retard ionosphérique estimé associé au satellite "s" le long
de la ligne de base entre la station itinérante et la première station de base.
46. Appareil de la revendication 44, dans lequel la correction apportée aux résidus associés
au satellite "s" dans le troisième ensemble de résidus et/ou le troisième ensemble
de résidus basés sur la phase de porteuse est liée à la quantité
où
est le deuxième différentiel de retard ionosphérique associé au satellite "s", et
est un différentiel de retard ionosphérique estimé associé au satellite "s" le long
de la ligne de base entre la station itinérante et la première station de base.
47. Appareil de la revendication 44, dans lequel le différentiel de retard ionosphérique
à partir du premier ensemble et associé au satellite "s" peut être indiqué par
dans lequel le différentiel de retard ionosphérique à partir du deuxième ensemble
et associé au satellite "s" peut être indiqué par
dans lequel les emplacements des première, deuxième et troisième stations de base
peuvent être représentés par les vecteurs X
1, X
2 et X
3, et dans lequel l'emplacement estimé de la station itinérante peut être représenté
par
X0,k,
dans lequel les corrections apportées à l'un ou plusieurs des résidus associés au
satellite "s" sont liées à une quantité
où
où α et β sont des constantes qui satisfont les relations :
où la notation {*}
n indique la composante de la quantité entre crochets le long de la direction nord,
où la notation {*}
e indique la composante de la quantité entre crochets le long de la direction est.
48. Appareil de la revendication 44, dans lequel la correction apportée aux résidus associés
au satellite "s" dans le deuxième ensemble de résidus et/ou le deuxième ensemble de
résidus basés sur la phase de porteuse est liée à la quantité
où
est le premier différentiel de retard ionosphérique associé au satellite "s".
49. Appareil de la revendication 44, dans lequel la correction apportée au résidu associé
au satellite "s" dans le troisième ensemble de résidus et/ou le troisième ensemble
de résidus basés sur la phase de porteuse est liée à la quantité
où
est le deuxième différentiel de retard ionosphérique associé au satellite "s".
50. Appareil selon la revendication 43 comprenant en outre :
un moyen pour modifier un ou plusieurs des résidus ci-dessus pour qu'il(s) dépende(nt)
des deuxièmes effets d'ordre dans les corrections de retard ionosphérique appliquées
aux lignes de base associées à la station itinérante, et
un moyen pour générer une estimation des deuxièmes effets d'ordre, et
dans lequel le moyen (i) de génération de l'estimation de l'emplacement de la station
itinérante génère l'estimation davantage à partir des deuxièmes effets d'ordre estimés.
51. Dispositif selon la revendication 43, dans lequel l'appareil génère le premier ensemble
de premiers différentiels de retard ionosphérique et le deuxième ensemble de deuxièmes
différentiels de retard ionosphérique à partir d'au moins les données de navigation
qu'il reçoit à partir des stations base.
52. Appareil selon la revendication 43 comprenant en outre :
un moyen pour générer une estimation initiale du premier ensemble de premiers différentiels
de retard ionosphérique associé aux signaux satellites reçus le long de la ligne de
base formée par les première et deuxième stations de base ;
un moyen pour générer une estimation initiale du deuxième ensemble de deuxièmes différentiels
de retard ionosphérique associé aux signaux satellites reçus le long de la ligne de
base formée par les première et troisième stations de base ;
un moyen pour générer une estimation initiale d'un troisième ensemble de troisièmes
différentiels de retard ionosphérique associé aux signaux satellites reçus le long
de la ligne de base formée par les deuxième et troisième stations de base ; et
un moyen pour générer des estimations finales des différentiels de retard ionosphérique
de telle sorte que la somme des estimations finales des premier, deuxième et troisième
différentiels de retard ionosphérique pour au moins un satellite "s" autour d'une
boucle de la station de base soit essentiellement égale à zéro.
53. Appareil de la revendication 35, dans lequel le moyen d'obtention du premier ensemble
d'ambiguïtés de cycle de phase de porteuse de satellite comprend un moyen de génération
du premier ensemble d'ambiguïtés de cycle de phase de porteuse de satellite à partir
d'au moins les emplacements des stations de base, et les données de navigation par
satellite mesurées telles que reçues par les stations de base.
54. Appareil de la revendication 36, dans lequel le moyen d'obtention des premier et deuxième
ensembles d'ambiguïtés de cycle de phase de porteuse de satellite comprend un moyen
de génération du premier ensemble d'ambiguïtés de cycle de phase de porteuse de satellite
à partir d'au moins les emplacements des première et deuxième stations de base et
des données de navigation par satellite mesurées telles que reçues par les première
et deuxième stations de base, et un moyen de génération du deuxième ensemble d'ambiguïtés
de cycle de phase de porteuse de satellite à partir d'au moins les emplacements des
première et troisième stations de base et des données de navigation par satellite
mesurées telles que reçues par les première et troisième stations de base.